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JavaScript Function.length property
  • Last Updated : 28 Aug, 2020
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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.

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



Example 1:




<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" 
        content="width=device-width,
                initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // Creating function name func
    // When no parameters are given
    function func1(){}
    console.log(
"The number of paramters required by "+
     "the function are: ", func1.length)
  </script>
</body>
</html>

Output:

Example 2:

When number of parameters is greater than one.




<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" 
        content="width=device-width,
                 initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // Creating function name func
    // When one parameters are given
    function func1(a){}
    console.log(
"The number of paramters required by the func1 are: ",
  func1.length)
    // When two parameters are given
    function func2(a, b){}
    console.log(
"The number of paramters required by the func2 are: ",
 func2.length)
    // When three parameters are given
    function func3(a, b, c){}
    console.log(
"The number of paramters required by the func3 are: ",
 func3.length)
    // When four parameters are given
    function func4(a, b, c, d){}
    console.log(
"The number of paramters required by the func4 are: ",
 func4.length)
  </script>
</body>
</html>

Output:

Example 3:

When array of arguments is given




<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" 
        content="width=device-width,
                 initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    // Creating function name func
    // When array of arguments are given
    function func4(...args){}
    console.log(
"The number of paramters required by the func4 are: ",
 func4.length)
  </script>
</body>
</html>

Output:

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