In ServiceNow Client Scripts, the control parameter denotes the field element (HTML control) that causes an onChange event. When you construct an onChange Client Script, the control parameter is immediately supplied to the function, allowing you to interact with the field that caused the event.
Here's a summary of how control works, its uses, and examples that demonstrate its application:
Understanding Control Parameter in Client Scripts
In a onChange Client Script, you write a function with four parameters: control, oldValue, newValue, and isLoading. The control argument specifies the HTML element of the field where the change occurred. This allows you to manipulate the field in the form without having to type its name.
Benefits of Using Control
Direct Reference: Instead of referring to a field by its variable name (such as g_form.getValue()), control allows you to interact with it directly.
Enhanced Readability: It improves code readability by eliminating the requirement to call g_form.getValue() or g_form.getControl().
Contextual Actions: You can use behavior or styling directly on the triggering field.
Example Use Cases of control
- Changing Styles Dynamically You can change the style of a field based on user input.
Example: Highlighting Field with New Value
In this example, if the newValue is set to "Critical," the field background color will change to red. This is useful for visually alerting users to critical information.
- Displaying tooltips or messages based on field values You can give users hints or feedback right on the field itself.
Example: Displaying Tooltips on Specific Conditions
In this script, when the newValue is "high," a tooltip is added, guiding the user to verify the priority setting.
- Enabling or disabling fields dynamically. Fields can be enabled or disabled based on changes in other fields, and you can dynamically reference individual fields with control.
Example: Enable field only if condition is met.
Here, the description field is enabled only if the triggering field's value is set to "Approved."
Additional Tips for Using control
- Access HTML Attributes: You can directly access HTML attributes like style, title, disabled, etc., to manipulate the field visually or functionally.
- Event Handling: You can attach event listeners to control if you need more complex interactions, though this is rarely necessary in ServiceNow.
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