Lecture 139:- Function Expressions

A function expression is another way to define a function in JavaScript. Unlike function declarations, which define a named function, function expressions define functions as unnamed expressions and assign them to variables.

Here's an example of a function expression:

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const addNumbers = function(x, y) {  return x + y; }

In the above example, we define a function expression and assign it to a variable called addNumbers. This variable can be used to call the function just like a regular named function:

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console.log(addNumbers(2, 3)); // output: 5

Function expressions can also be used as arguments to other functions, or returned as the result of a function call. They are often used to create anonymous functions on-the-fly or to create functions with dynamic behavior.

One common use of function expressions is with event listeners in web development. Here's an example of attaching a click event listener to a button element using a function expression:

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<button id="myButton">Click Me!</button> <script>  const button = document.querySelector('#myButton');  button.addEventListener('click', function() {    alert('Button clicked!');  }); </script>

In the above example, we use a function expression to define an anonymous function that is called when the button is clicked. This allows us to specify the behavior of the button without having to define a separate named function.