1. Checking Form Type

The form type indicates whether the form is in create, update, read-only, or another mode.

function checkFormType(executionContext) {
    var formContext = executionContext.getFormContext();
    var formType = formContext.ui.getFormType(); // Get the form type
    
    // Form types: 1 = Create, 2 = Update, 3 = Read Only, 4 = Disabled, 6 = Bulk Edit
    switch (formType) {
        case 1:
            console.log("This is a Create form");
            break;
        case 2:
            console.log("This is an Update form");
            break;
        case 3:
            console.log("This is a Read-Only form");
            break;
        default:
            console.log("Other form type: " + formType);
    }
}

2. Checking Form State (Dirty Check)

Check if the form has unsaved changes (i.e., is "dirty").

function checkFormState(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Check if the form has unsaved changes
    if (formContext.data.entity.getIsDirty()) {
        console.log("Form has unsaved changes!");
    } else {
        console.log("Form is clean (no unsaved changes).");
    }
}

3. Getting and Setting Field Data

Below are examples for getting and setting values for different field types on the Account form.

a. Single Line of Text (e.g., "name")

function handleTextField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the value of the Account Name field
    var accountName = formContext.getAttribute("name").getValue();
    console.log("Account Name: " + accountName);
    
    // Set a new value for the Account Name field
    formContext.getAttribute("name").setValue("New Account Name");
}

b. Option Set (e.g., "accountcategorycode")

function handleOptionSet(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the selected value of the Category field (returns integer)
    var category = formContext.getAttribute("accountcategorycode").getValue();
    console.log("Category Value: " + category); // e.g., 1 = Preferred Customer
    
    // Set a new value (use a valid option set value)
    formContext.getAttribute("accountcategorycode").setValue(2); // 2 = Standard
}

c. Lookup Field (e.g., "primarycontactid")

function handleLookupField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the value of the Primary Contact lookup
    var primaryContact = formContext.getAttribute("primarycontactid").getValue();
    if (primaryContact) {
        console.log("Primary Contact ID: " + primaryContact[0].id);
        console.log("Primary Contact Name: " + primaryContact[0].name);
    }
    
    // Set a new value for the Primary Contact lookup
    var lookupValue = [{
        id: "{GUID-OF-CONTACT}", // Replace with a valid Contact GUID
        entityType: "contact",
        name: "John Doe"
    }];
    formContext.getAttribute("primarycontactid").setValue(lookupValue);
}

d. Date Field (e.g., "createdon")

function handleDateField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Created On date value
    var createdOn = formContext.getAttribute("createdon").getValue();
    console.log("Created On: " + createdOn);
    
    // Set a new date value (e.g., today's date)
    var today = new Date();
    formContext.getAttribute("createdon").setValue(today);
}

e. Currency Field (e.g., "revenue")

function handleCurrencyField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Annual Revenue value
    var revenue = formContext.getAttribute("revenue").getValue();
    console.log("Annual Revenue: " + revenue);
    
    // Set a new value for Annual Revenue
    formContext.getAttribute("revenue").setValue(50000.00); // Set to 50,000
}

f. Two Options (Boolean) (e.g., "donotemail")

function handleBooleanField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Do Not Email value (true/false)
    var doNotEmail = formContext.getAttribute("donotemail").getValue();
    console.log("Do Not Email: " + doNotEmail);
    
    // Set a new value (true = Yes, false = No)
    formContext.getAttribute("donotemail").setValue(true); // Set to Yes
}

g. Multi-Select Option Set (e.g., custom field "new_multiselect")

function handleMultiSelect(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the selected values of a multi-select option set
    var multiSelect = formContext.getAttribute("new_multiselect").getValue();
    console.log("Selected Values: " + multiSelect); // Returns array of integers
    
    // Set new values (array of valid option set values)
    formContext.getAttribute("new_multiselect").setValue([100000001, 100000002]);
}

4. Showing/Hiding Fields

Control the visibility of fields based on conditions.

function toggleFieldVisibility(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Check if Account Name is populated
    if (formContext.getAttribute("name").getValue()) {
        formContext.getControl("telephone1").setVisible(true); // Show Telephone
    } else {
        formContext.getControl("telephone1").setVisible(false); // Hide Telephone
    }
}

5. Enabling/Disabling Fields

Make fields editable or read-only dynamically.

function toggleFieldEnabled(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Disable the Telephone field if Revenue is less than 10000
    var revenue = formContext.getAttribute("revenue").getValue();
    if (revenue < 10000) {
        formContext.getControl("telephone1").setDisabled(true); // Disable field
    } else {
        formContext.getControl("telephone1").setDisabled(false); // Enable field
    }
}

6. Setting Field Requirement Level

Dynamically set a field as required, recommended, or optional.

function setFieldRequirement(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Set Telephone as required if Category is "Preferred Customer" (value = 1)
    var category = formContext.getAttribute("accountcategorycode").getValue();
    if (category === 1) {
        formContext.getAttribute("telephone1").setRequiredLevel("required");
    } else {
        formContext.getAttribute("telephone1").setRequiredLevel("none");
    }
}

7. Refreshing the Form

Refresh the form data without reloading the entire page.

function refreshForm(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Refresh form data from the server
    formContext.data.refresh(true).then(
        function() { console.log("Form refreshed successfully"); },
        function(error) { console.log("Error refreshing form: " + error.message); }
    );
}

8. Saving the Form

Force the form to save programmatically.

function saveForm(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Save the form
    formContext.data.save().then(
        function() { console.log("Form saved successfully"); },
        function(error) { console.log("Error saving form: " + error.message); }
    );
}

9. Switching Forms

Navigate to a different form based on a condition (assuming multiple forms exist for the Account entity).

function switchForm(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get available forms
    var forms = formContext.ui.formSelector.items.get();
    
    // Switch to a specific form (e.g., "Information" form) if condition met
    var revenue = formContext.getAttribute("revenue").getValue();
    if (revenue > 100000) {
        for (var i in forms) {
            if (forms[i].getLabel() === "Information") {
                forms[i].navigate(); // Switch to the "Information" form
                break;
            }
        }
    }
}

10. Adding Form Notifications

Display a notification on the form.

function addNotification(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Add a warning notification if Revenue is null
    if (!formContext.getAttribute("revenue").getValue()) {
        formContext.ui.setFormNotification(
            "Please enter the Annual Revenue.", // Message
            "WARNING",                         // Level: INFO, WARNING, ERROR
            "revenueNotification"              // Unique ID for the notification
        );
    } else {
        formContext.ui.clearFormNotification("revenueNotification"); // Clear notification
    }
}

More:

1. Show/Hide a Section

Show or hide a section (e.g., "General" section) based on a condition.

function toggleSectionVisibility(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the section by its name (e.g., "General" section in a tab)
    var section = formContext.ui.tabs.get("tab_general").sections.get("section_general");
    
    // Show section if Revenue > 10000, hide otherwise
    var revenue = formContext.getAttribute("revenue").getValue();
    if (revenue > 10000) {
        section.setVisible(true); // Show the section
    } else {
        section.setVisible(false); // Hide the section
    }
}

2. Show/Hide a Tab

Show or hide an entire tab (e.g., "Details" tab) based on a condition.

function toggleTabVisibility(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the tab by its name (e.g., "tab_details")
    var tab = formContext.ui.tabs.get("tab_details");
    
    // Show tab if Category is "Preferred Customer" (value = 1), hide otherwise
    var category = formContext.getAttribute("accountcategorycode").getValue();
    if (category === 1) {
        tab.setVisible(true); // Show the tab
    } else {
        tab.setVisible(false); // Hide the tab
    }
}

3. Expand/Collapse a Tab

Expand or collapse a tab programmatically.

function toggleTabExpansion(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the tab by its name (e.g., "tab_summary")
    var tab = formContext.ui.tabs.get("tab_summary");
    
    // Expand tab if form is in Create mode (formType = 1)
    if (formContext.ui.getFormType() === 1) {
        tab.setDisplayState("expanded"); // Expand the tab
    } else {
        tab.setDisplayState("collapsed"); // Collapse the tab
    }
}

4. Lock/Unlock All Fields in a Section

Enable or disable all fields within a specific section.

function lockSectionFields(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the section (e.g., "section_contact_info" in "tab_general")
    var section = formContext.ui.tabs.get("tab_general").sections.get("section_contact_info");
    
    // Iterate through all controls in the section
    section.controls.forEach(function(control) {
        // Disable fields if Account Name is not set
        if (!formContext.getAttribute("name").getValue()) {
            control.setDisabled(true); // Disable the control
        } else {
            control.setDisabled(false); // Enable the control
        }
    });
}

5. Dynamically Populate Option Set Values

Add or remove options in an option set dynamically.

function populateOptionSet(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the option set control (e.g., "industrycode")
    var optionSetControl = formContext.getControl("industrycode");
    
    // Clear existing options
    optionSetControl.clearOptions();
    
    // Add custom options dynamically
    optionSetControl.addOption({ text: "Technology", value: 1 });
    optionSetControl.addOption({ text: "Finance", value: 2 });
    optionSetControl.addOption({ text: "Healthcare", value: 3 });
}

6. Retrieve Related Record Data (e.g., Primary Contact)

Use Web API to fetch data from a related record.

function fetchRelatedContact(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Primary Contact lookup value
    var primaryContact = formContext.getAttribute("primarycontactid").getValue();
    if (primaryContact) {
        var contactId = primaryContact[0].id.replace("{", "").replace("}", "");
        
        // Use Web API to retrieve contact's email
        Xrm.WebApi.retrieveRecord("contact", contactId, "?$select=emailaddress1").then(
            function(result) {
                console.log("Contact Email: " + result.emailaddress1);
                // Optionally set a field with the retrieved value
                formContext.getAttribute("emailaddress1").setValue(result.emailaddress1);
            },
            function(error) {
                console.log("Error fetching contact: " + error.message);
            }
        );
    }
}

7. Prevent Form Save

Block form save if a condition is not met.

function preventSave(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Prevent save if Telephone is empty
    if (!formContext.getAttribute("telephone1").getValue()) {
        executionContext.getEventArgs().preventDefault(); // Block the save
        formContext.ui.setFormNotification(
            "Telephone is required before saving.",
            "ERROR",
            "telephoneError"
        );
    } else {
        formContext.ui.clearFormNotification("telephoneError");
    }
}

8. Filter Lookup Field Options

Apply a custom filter to a lookup field (e.g., filter Primary Contact by Account).

function filterLookup(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Define a fetchXML filter to show only contacts related to this account
    var accountId = formContext.data.entity.getId().replace("{", "").replace("}", "");
    var fetchXml = "";
    
    // Apply the filter to the Primary Contact lookup
    formContext.getControl("primarycontactid").addCustomFilter(fetchXml, "contact");
}

9. Calculate Field Value (e.g., Total Revenue)

Calculate a value based on other fields and update a field.

function calculateTotalRevenue(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get values from fields (e.g., revenue and a custom field "new_additionalrevenue")
    var revenue = formContext.getAttribute("revenue").getValue() || 0;
    var additionalRevenue = formContext.getAttribute("new_additionalrevenue").getValue() || 0;
    
    // Calculate total
    var totalRevenue = revenue + additionalRevenue;
    
    // Set the total to a custom field (e.g., "new_totalrevenue")
    formContext.getAttribute("new_totalrevenue").setValue(totalRevenue);
}

10. Open a Custom HTML Dialog

Display a custom dialog box with HTML content.

function openCustomDialog(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Define custom HTML content
    var dialogContent = "

";
    
    // Define dialog options
    var dialogOptions = {
        height: 300,
        width: 400
    };
    
    // Open the dialog
    Xrm.Navigation.openAlertDialog({ text: dialogContent, confirmButtonLabel: "OK" }, dialogOptions);
}

Advanced:

1. Refresh a Subgrid

Refresh a subgrid (e.g., Contacts subgrid) to reflect updated data.

function refreshSubgrid(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the subgrid control (e.g., "Contacts" subgrid)
    var subgrid = formContext.getControl("Contacts");
    
    if (subgrid) {
        // Refresh the subgrid
        subgrid.refresh();
        console.log("Contacts subgrid refreshed.");
    } else {
        console.log("Subgrid not found or not loaded yet.");
    }
}

2. Add a Custom Button to a Subgrid

Add a custom button to a subgrid’s command bar (requires ribbon customization).

function addCustomSubgridButton(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Note: This requires Ribbon Workbench or similar to add the button
    // Sample action when custom button is clicked
    function customButtonAction() {
        var subgrid = formContext.getControl("Contacts");
        if (subgrid) {
            var selectedRecords = subgrid.getGrid().getSelectedRows();
            console.log("Selected Contacts: " + selectedRecords.getLength());
        }
    }
    
    // Placeholder for triggering the custom action
    console.log("Custom button action ready. Configure via Ribbon Workbench.");
}

3. Validate Subgrid Records

Prevent form save if a subgrid (e.g., Contacts) has fewer than a minimum number of records.

function validateSubgridRecords(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Contacts subgrid
    var subgrid = formContext.getControl("Contacts");
    
    if (subgrid) {
        var gridRows = subgrid.getGrid().getTotalRecordCount();
        if (gridRows < 2) {
            executionContext.getEventArgs().preventDefault(); // Block save
            formContext.ui.setFormNotification(
                "At least 2 contacts are required.",
                "ERROR",
                "subgridValidation"
            );
        } else {
            formContext.ui.clearFormNotification("subgridValidation");
        }
    }
}

4. Open a Quick Create Form

Open a quick create form for a related entity (e.g., Contact) from the Account form.

function openQuickCreateContact(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Define quick create parameters
    var quickCreateParams = {
        entityName: "contact",
        defaultValues: {
            parentcustomerid: {
                id: formContext.data.entity.getId(),
                entityType: "account",
                name: formContext.getAttribute("name").getValue()
            }
        }
    };
    
    // Open the quick create form
    Xrm.Navigation.openForm(quickCreateParams).then(
        function() { console.log("Quick create form opened."); },
        function(error) { console.log("Error: " + error.message); }
    );
}

5. Set Default Values Based on Form Type

Set default field values when the form is in Create mode.

function setDefaultValues(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Check if form is in Create mode (formType = 1)
    if (formContext.ui.getFormType() === 1) {
        // Set default values
        formContext.getAttribute("accountcategorycode").setValue(1); // Preferred Customer
        formContext.getAttribute("donotemail").setValue(false); // Allow Email
        console.log("Default values set for new account.");
    }
}

6. Copy Field Value to Another Field

Copy a field value (e.g., Main Phone to Fax) when a condition is met.

function copyPhoneToFax(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Copy Telephone to Fax if Fax is empty
    var phone = formContext.getAttribute("telephone1").getValue();
    var fax = formContext.getAttribute("fax").getValue();
    
    if (phone && !fax) {
        formContext.getAttribute("fax").setValue(phone);
        console.log("Telephone copied to Fax.");
    }
}

7. Highlight a Field Based on Value

Change a field’s background color based on its value (requires CSS injection).

function highlightField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Revenue field control
    var revenueControl = formContext.getControl("revenue");
    var revenueValue = formContext.getAttribute("revenue").getValue();
    
    // Apply custom CSS based on value
    if (revenueValue > 100000) {
        revenueControl.getAttribute().fireOnChange(); // Ensure UI updates
        revenueControl.getControl().getElement().style.backgroundColor = "#90EE90"; // Light green
    } else {
        revenueControl.getControl().getElement().style.backgroundColor = ""; // Reset
    }
}

8. Execute a Workflow Programmatically

Trigger a workflow for the current record using Web API.

function triggerWorkflow(executionContext) {
    var formContext = executionContext.getFormContext();
    var recordId = formContext.data.entity.getId().replace("{", "").replace("}", "");
    
    // Workflow ID (replace with actual workflow GUID)
    var workflowId = "{YOUR-WORKFLOW-GUID}";
    
    // Execute workflow via Web API
    var request = {
        entity: { entityType: "account", id: recordId },
        workflowId: workflowId
    };
    
    Xrm.WebApi.online.execute(request).then(
        function() { console.log("Workflow executed successfully."); },
        function(error) { console.log("Error executing workflow: " + error.message); }
    );
}

9. Check User Security Roles

Perform actions based on the user’s security roles.

function checkUserRoles(executionContext) {
    var formContext = executionContext.getFormContext();
    var userRoles = Xrm.Utility.getGlobalContext().userSettings.roles;
    
    // Check if user has a specific role (e.g., "System Administrator")
    var hasAdminRole = false;
    userRoles.forEach(function(role) {
        if (role.name === "System Administrator") {
            hasAdminRole = true;
        }
    });
    
    // Show a section only for admins
    var section = formContext.ui.tabs.get("tab_general").sections.get("section_admin");
    section.setVisible(hasAdminRole);
    console.log("Admin role check: " + hasAdminRole);
}

10. Auto-Generate Account Number

Generate a unique account number based on a prefix and counter.

function generateAccountNumber(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Only generate on Create form
    if (formContext.ui.getFormType() === 1) {
        var accountName = formContext.getAttribute("name").getValue();
        if (accountName) {
            // Simple logic: Prefix + random number
            var prefix = "ACC-";
            var randomNum = Math.floor(1000 + Math.random() * 9000); // 4-digit random
            var accountNumber = prefix + randomNum;
            
            // Set the account number field (e.g., "accountnumber")
            formContext.getAttribute("accountnumber").setValue(accountNumber);
            console.log("Generated Account Number: " + accountNumber);
        }
    }
}

Advanced:

1. Dynamic Form Navigation

Redirect users to a specific tab or section based on field values.

function navigateFormDynamically(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the revenue value
    var revenue = formContext.getAttribute("revenue").getValue() || 0;
    
    // Navigate to appropriate tab based on revenue
    if (revenue > 100000) {
        formContext.ui.tabs.get("tab_details").setFocus(); // Focus on Details tab
        formContext.ui.tabs.get("tab_details").setDisplayState("expanded");
        console.log("Navigated to Details tab for high revenue.");
    } else {
        formContext.ui.tabs.get("tab_general").setFocus(); // Focus on General tab
        formContext.ui.tabs.get("tab_general").setDisplayState("expanded");
        console.log("Navigated to General tab for low revenue.");
    }
}

2. Real-Time Field Validation

Validate field formats (e.g., email) in real-time using regular expressions.

function validateEmailField(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the email field value
    var email = formContext.getAttribute("emailaddress1").getValue();
    var emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/; // Basic email regex
    
    // Validate and show notification
    if (email && !emailRegex.test(email)) {
        formContext.getControl("emailaddress1").setNotification(
            "Please enter a valid email address.",
            "emailValidation"
        );
    } else {
        formContext.getControl("emailaddress1").clearNotification("emailValidation");
    }
}

3. Integration with External APIs

Call an external API to fetch data (e.g., company info from a public API).

function fetchExternalData(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the account name to use in the API call
    var accountName = formContext.getAttribute("name").getValue();
    if (!accountName) return;
    
    // Example: Call a dummy external API (replace with real endpoint)
    var apiUrl = "https://api.example.com/company?name=" + encodeURIComponent(accountName);
    
    fetch(apiUrl, {
        method: "GET",
        headers: { "Content-Type": "application/json" }
    })
    .then(response => response.json())
    .then(data => {
        // Assuming the API returns revenue data
        formContext.getAttribute("revenue").setValue(data.revenue || 0);
        console.log("External data fetched: " + JSON.stringify(data));
    })
    .catch(error => {
        console.log("Error fetching external data: " + error.message);
    });
}

4. Custom Grid Filtering

Apply an advanced filter to a subgrid (e.g., show only active contacts).

function filterSubgrid(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Get the Contacts subgrid
    var subgrid = formContext.getControl("Contacts");
    
    if (subgrid) {
        // Define FetchXML to filter active contacts only
        var fetchXml = "";
        
        // Apply the filter
        subgrid.setFilterXml(fetchXml);
        subgrid.refresh();
        console.log("Subgrid filtered to show only active contacts.");
    }
}

5. Form Timer

Display a countdown timer or track time spent on the form.

function startFormTimer(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Initialize timer (in seconds)
    var timeSpent = 0;
    
    // Update timer every second
    var timer = setInterval(function() {
        timeSpent++;
        var minutes = Math.floor(timeSpent / 60);
        var seconds = timeSpent % 60;
        var timeDisplay = minutes + "m " + seconds + "s";
        
        // Display time in a custom field or notification
        formContext.ui.setFormNotification(
            "Time spent on form: " + timeDisplay,
            "INFO",
            "timerNotification"
        );
    }, 1000);
    
    // Optional: Stop timer on save (call this in OnSave event)
    // clearInterval(timer);
}

6. Bulk Field Updates

Update multiple fields at once based on a single condition.

function bulkFieldUpdate(executionContext) {
    var formContext = executionContext.getFormContext();
    
    // Check if Category is "Preferred Customer" (value = 1)
    var category = formContext.getAttribute("accountcategorycode").getValue();
    if (category === 1) {
        // Bulk update fields
        formContext.getAttribute("creditlimit").setValue(100000); // Set Credit Limit
        formContext.getAttribute("donotemail").setValue(false); // Allow Email
        formContext.getAttribute("donotphone").setValue(false); // Allow Phone
        console.log("Bulk updated fields for Preferred Customer.");
    }
}

7. Custom Error Handling

Create a centralized error logging mechanism for form scripts.

function customErrorHandler(executionContext, functionName, error) {
    var formContext = executionContext.getFormContext();
    
    // Log error details
    var errorMessage = "Error in " + functionName + ": " + error.message;
    console.error(errorMessage);
    
    // Display error to user
    formContext.ui.setFormNotification(
        "An error occurred: " + error.message + ". Please contact support.",
        "ERROR",
        "error_" + functionName
    );
    
    // Optional: Log to a custom entity via Web API
    var errorLog = {
        "new_errorname": functionName,
        "new_errormessage": error.message,
        "new_timestamp": new Date().toISOString()
    };
    Xrm.WebApi.createRecord("new_errorlog", errorLog).then(
        function() { console.log("Error logged to custom entity."); },
        function(err) { console.log("Failed to log error: " + err.message); }
    );
}

// Example usage in another function
function sampleFunction(executionContext) {
    try {
        var formContext = executionContext.getFormContext();
        var invalidField = formContext.getAttribute("nonexistent_field").getValue(); // Will throw error
    } catch (error) {
        customErrorHandler(executionContext, "sampleFunction", error);
    }
}

Notes: 

• Always pass executionContext as a parameter to access formContext. Enable the "Pass execution context as first parameter" option when registering the script in the form event handler.

Business Rule vs JavaScript