What is the use of callback function in Clientscript and its limitations?

[trucntaku]

Are you referring to the callback function that passed as parameter to onCellEdit()? There is a documentation on it https://docs.servicenow.com/bundle/utah-application-development/page/script/client-scripts/concept/c.... 

A callback function can be used to perform additional actions or logic after a specific event or action has been executed. The purpose of a callback function is to provide a way to handle asynchronous operations or customize behavior based on the outcome of a particular action.  

[Rohan Gladman]

One limitation is that it will always execute as the user who is logged in.

So if you're hoping to retrieve value from a table/field they don't have read access to, then it will fail.

VS

Script include can be called with the security of a specified user that does have access.. saves you having to punch holes in your ACLs.   

[Maddysunil]

@kaeunakar 

a callback function in Client Scripts is a JavaScript function that gets executed in response to a specific event on a form or a field. These functions are commonly used to perform actions such as validating user input, dynamically updating fields, or triggering server-side actions.

Here's how callbacks work and their common uses:

1. onChange: This callback function is triggered when the value of a field changes. It's commonly used to validate input or perform calculations based on the new value.

2. onBlur: This callback function is triggered when a field loses focus, meaning the user moves away from it after interacting with it. It's often used for validation purposes, similar to onChange.

3. onLoad: This callback function is executed when the form or page loads. It's used to initialize fields, set default values, or perform any other actions that need to happen when the form is first displayed.

4. onSubmit: This callback function is triggered when the form is submitted, typically by clicking a submit button. It's used to perform final validation checks before data is sent to the server.

5. onCellEdit: This callback function is specific to List v3, and it's triggered when a cell in a list is edited. It's used for handling changes in list data.

6. onChangeClient: This callback function is similar to onChange but is specifically used in catalog client scripts.

Limitations of callback functions in Client Scripts:

1. Client-side Execution Only: Callback functions in Client Scripts run entirely on the client-side within the user's browser. They cannot directly interact with server-side resources or perform server-side actions.

2. Limited Scope: Callback functions are limited to the form or field context in which they are defined. They cannot access data outside of this context unless explicitly provided.

3. Browser Compatibility: The behavior of callback functions may vary slightly across different web browsers. It's essential to test them thoroughly to ensure consistent behavior.

4. Performance Concerns: Excessive use of callback functions or inefficient JavaScript code can impact the performance of the ServiceNow instance, particularly for users on slower devices or with limited network connectivity.

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Thanks