Function Expression allows us to create an anonymous function which doesn’t have any function name which is the main difference between Function Expression and Function Declaration. A function expression can be used as an IIFE (Immediately Invoked Function Expression)which runs as soon as it is defined. A function expression has to be stored in a variable and can be accessed using variableName. With the ES6 features introducing Arrow Function, it becomes more easier to declare function expression.
Syntax for Function Declaration:
function functionName(x, y) { statements... return (z) };
Syntax for Function Expression (anonymous) :
let variableName = function(x, y) { statements... return (z) };
Syntax for Function Expression (named) :
let variableName = function functionName(x, y)
{ statements... return (z) };
Syantax for Arrow Function:
let variableName = (x, y) => { statements... return (z) };
Note:
- A function expression has to be defined first before calling it or using it as a parameter.
- An arrow function must have an return statement.
Below examples illustrate the funcion expression in JavaScript:
Example 1: Code for Function Declaration.
Javascript
<script> function callAdd(x, y){ let z = x + y; return z; } console.log("Addition : " + callAdd(7, 4)); </script> |
Output:
Addition : 11
Example 2: Code for Function Expression (anonymous)
Javascript
<script> var calSub = function(x, y){ let z = x - y; return z; } console.log("Subtration : " + calSub(7, 4)); </script> |
Output:
Subtration : 3
Example 3: Code for Function Expression (named)
Javascript
<script> var calMul = function Mul(x, y){ let z = x * y; return z; } console.log("Multiplication : " + calMul(7, 4)); </script> |
Output:
Multiplication : 28
Example 4: Code for Arrow Function
Javascript
<script> var calDiv = (x, y) => { let z = x / y; return z; } console.log("Division : " + calDiv(24, 4)); </script> |
Output:
Division : 6
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