JavaScript | boolean.valueOf() function

The Boolean.valueOf() is an inbuilt function in javascript which is used to return a boolean value either “true” or “false” depending upon the value of the specified boolean object.
It returns false if the string argument is null otherwise it returns true.

Syntax:

boolean.valueOf()

Parameter: This function deoes not accepts any parameter.



Return value: It returns a boolean value either “true” or “false” depending upon the value of the specified boolean object.

Let’s see some JavaScript code on this boolean.toString() function:

  • Example 1:
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    <script>
    // Here Boolean object obj is created 
    // for the value true.
    var obj = new Boolean(true);
      
    // Here boolean.valueOf() function is 
    // used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    true
  • Example 2:
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    <script>
    // Here Boolean object obj is
    // created for the value 1.
    var obj = new Boolean(1);
      
    // Here boolean.valueOf() function 
    // is used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    true
  • Example 3:
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    <script>
    // Here Boolean object obj is 
    // created for the value -1.
    var obj = new Boolean(-1);
      
    // Here boolean.valueOf() function
    // is used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    true
  • Example 4:
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    <script>
    // Here Boolean object obj is 
    // created for the value 1.2
    var obj = new Boolean(1.2);
      
    // Here boolean.valueOf() function 
    // is used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    true
  • Example 5:
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    <script>
    // Here Boolean object obj is 
    // created for the value as string "gfg"
    var obj = new Boolean("gfg");
      
    // Here boolean.valueOf() function is 
    // used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    true
  • Example 6:
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    <script>
    // Here Boolean object obj is created for the value false.
    var obj = new Boolean(false);
      
    // Here boolean.valueOf() function is
    // used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    false
  • Example 7:
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    <script>
    // Here Boolean object obj is created 
    // for the value zero (0)
    var obj = new Boolean(0);
      
    // Here boolean.valueOf() function is 
    // used for the created object obj.
    document.write(obj.valueOf());
    </script>

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    Output:

    false
    1. Errors and Exceptions: Check the console for this examples.

    2. Example 1: Here the value as geeksforgeeks gives an error because this value is not defined only true and false has been predefined.
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      <script>
      // Here Boolean object obj is created 
      // for the value geeksforgeeks.
      var obj = new Boolean(geeksforgeeks);
        
      // Here boolean.valueOf() function is
      // used for the created object obj.
      console.log(obj.valueOf());
      </script>

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      Output:

      Error: geeksforgeeks is not defined
    3. Example 2: Here complex number can not be taken as the parameter only integer values and string can be taken as the parameter that is why it returns error.
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      <script>
      // Here Boolean object obj is created 
      // for the value such as complex number 1+2i
      var obj = new Boolean(1 + 2i);
        
      // Here boolean.valueOf() function is
      // used for the created object obj.
      console.log(obj.valueOf());

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      Output:

      Error: Invalid or unexpected token

    Application:
    This function’s application is to return a boolean value of either “true” or “false” depending upon the value of the object given.
    Let’s see JavaScript program on this application:

  • Example 1:
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    <script>
    // Here Boolean object obj 
    // is created for the value 27
    var obj = new Boolean(27);
      
    // Here boolean.valueOf() function is 
    // used for the created object obj.
    document.write(obj.valueOf());

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    Output:

    true


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