The Javascript weakMap.has() is an inbuilt function in JavaScript that is used to return a boolean value which indicates whether an element with a particular key is present 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.

Below are examples of weakMap.has() method.

Example 1: Below is a basic example of weakmap.has() method that returns true.

function gfg() {
    const weakmap = new WeakMap();
    const key = {};
    weakmap.set(key, 'gfg');

    console.log(weakmap.has(key));
}
gfg();

true

Example 2: Here the output is false because the key "key1" has not been set at the end of the weakMap object. 

// 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
console.log(weakmap1.has(key1));

false

We have a complete list of Javascript WeakMap methods, to check those please go through Javascript WeakMap Complete reference article.

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