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JavaScript weakMap.has() Method

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  • Difficulty Level : Medium
  • Last Updated : 27 Oct, 2021
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Below is the example of weakMap.has() method.

  • Example:




    <script> 
        function gfg() { 
    const weakmap = new WeakMap(); 
    const key = {}; 
    weakmap.set(key, 'gfg'); 
      
    document.write(weakmap.has(key)); 
        
        gfg(); 
    </script> 

  • Output:
    true

The weakMap.has() is an inbuilt function in JavaScript which is used to return a boolean value which indicates whether an element with a particular key presents in the weakmap object or not.

Syntax:

weakMap.has(key);

Parameters: It accepts a parameter ‘key’ which is the key of the element which is going to be tested for presence in the object weakmap.

Return values: It returns true if the element with the specified key is present in the weakmap object otherwise it returns false.

Example:

Input: weakmap1.has(key1)
Output: true

JavaScripts to show the working of this function:
Code #1:




<script>
  
   // Creating a WeakMap() object
   const weakmap1 = new WeakMap();
     
   // Creating a key "key1"
   const key1 = {};
     
   // setting element 'gfg' to the key "key1"
   weakmap1.set(key1, 'gfg');
     
   // Testing whether the key is present 
   // in the weakMap() object or not
   document.write(weakmap1.has(key1));
  
</script>

Output:

true

Code #2:




<script>
  
   // Creating a WeakMap() object
   const weakmap1 = new WeakMap();
     
   // Creating a key "key1"
   const key1 = {};
     
   // Testing whether the key is present 
   // in the weakMap() object or not
   document.write(weakmap1.has(key1));
  
</script>

Output:

false

Here output is false because the key “key1” has not been set at the end of the weakMap object.

Supported Browsers:

  • Google Chrome 36 and above
  • Edge 12 and above
  • Firefox 6 and above
  • Internet Explorer 11 and above
  • Opera 23 and above
  • Safari 8 and above

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