JavaScript Function length property

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The Javascript Function.length property of the function object in Javascript is used to return the number of parameters required by a function.

Syntax:

function.length

Parameters: This method requires no parameters.

Return: Return type is number.

A few examples are given below for a better understanding of the method.

Example 1: When the number of parameters is zero.

Javascript

<script> 
    // Creating function name func 
    // When no parameters are given 
    function func1(){} 
    console.log( 
    "The number of parameters required by "+ 
     "the function are: ", func1.length) 
</script>

Output:

The number of parameters required by the function are:  0

Example 2: When the number of parameters is greater than one.

Javascript

<script> 
    // Creating function name func 
    // When one parameters are given 
    function func1(a){} 
    console.log( 
    "The number of parameters required by the func1 are: ", 
      func1.length) 
    // When two parameters are given 
    function func2(a, b){} 
    console.log( 
    "The number of parameters required by the func2 are: ", 
     func2.length) 
    // When three parameters are given 
    function func3(a, b, c){} 
    console.log( 
    "The number of parameters required by the func3 are: ", 
     func3.length) 
    // When four parameters are given 
    function func4(a, b, c, d){} 
    console.log( 
    "The number of parameters required by the func4 are: ", 
     func4.length) 
</script>

Output:

The number of parameters required by the func1 are:  1
The number of parameters required by the func2 are:  2
The number of parameters required by the func3 are:  3
The number of parameters required by the func4 are:  4

Example 3: When an array of arguments is given

Javascript

<script> 
    // Creating function name func 
    // When array of arguments are given 
    function func4(...args){} 
    console.log( 
    "The number of parameters required by the func4 are: ", 
     func4.length) 
</script>

Output:

The number of parameters required by the func4 are:  0

We have a complete list of Javascript Function methods, to check those please go through this Javascript Function Complete reference article.

Supported Browser:

Chrome 1 and above
Edge 12 and above
Firefox 1 and above
Internet Explorer 4 and above
Opera 3 and above
Safari 1 and above

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