JavaScript weakMap.has() Method

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