JavaScript | weakMap.has() with Examples

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.

JavaScripts to show the working of this function:

Code #1:

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<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>

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Output:

true

Code #2:

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<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>

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Output:

false

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



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