JavaScript: choosing between assigning to the callback function or using an anonymous function

Question

JavaScript: choosing between assigning to the callback function or using an anonymous function

MY CONCERN

I have been exploring AJAX fundamentals from various online sources. While grasping the multi-step process of sending an asynchronous HTTP request, I noticed a slight discrepancy in the way the usage of the .onload property is handled on the XHR request object, either being assigned to 1) an anonymous function or 2) a callback (as far as I interpret from MDN).

1ST METHOD

The .onload property is linked to the ourRequest object and is assigned to an anonymous function:

ourRequest.onload = function() { 
  // code implementation here
}

2ND METHOD

The .onload property is attached to the asyncRequestObject object and is set to refer to a function by its name (a callback?):

function handleSuccess () { 
  // code implementation here
}

asyncRequestObject.onload = handleSuccess;

MY QUERY

What distinguishes the functioning of the 1st and 2nd methods?

Additionally, is there a specific rationale behind preferring the 1st method over the 2nd?

javascript ajax callback onload anonymous-function

Answer 1

Answer №1

When a function is declared, it creates a variable within the current scope that bears the function's name and holds a reference to the function itself (which is hoisted).

A function expression, on the other hand, just evaluates to a reference to the function.

Essentially, the key distinction is that with handleSuccess, you can access the function for additional uses in different parts of your code.

Answer 2

When a function is declared, it creates a variable within the current scope that bears the function's name and holds a reference to the function itself (which is hoisted).

A function expression, on the other hand, just evaluates to a reference to the function.

Essentially, the key distinction is that with handleSuccess, you can access the function for additional uses in different parts of your code.

Answer 3

Answer №2

What is the distinction between the functionality of the first and second methods?

The key difference lies in the fact that the initial function is an anonymous function expression, while the latter is a named function. Both serve as event handlers for the "load" event of the XMLHttpRequest.

Is there a specific advantage to using the first method over the second?

If you do not intend to reuse your handler elsewhere, there is no necessity to define your function with a name.

It follows the standard programming principle of using variables/constants for recurring values and literals for one-time use cases.

Answer 4

What is the distinction between the functionality of the first and second methods?

The key difference lies in the fact that the initial function is an anonymous function expression, while the latter is a named function. Both serve as event handlers for the "load" event of the XMLHttpRequest.

Is there a specific advantage to using the first method over the second?

If you do not intend to reuse your handler elsewhere, there is no necessity to define your function with a name.

It follows the standard programming principle of using variables/constants for recurring values and literals for one-time use cases.

JavaScript: choosing between assigning to the callback function or using an anonymous function

MY CONCERN

1ST METHOD

2ND METHOD

MY QUERY

Answer №1

Answer №2

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