Javascript WeakMap has()

Introduction

The Javascript WeakMap has() method checks whether a key-value pair exists in the WeakMap object or not. 

wm.has(key);
Parameters Optional Meaning
key Not The key of the element

It returns true if an element with the key exists in the WeakMap object; otherwise false. 

let window = function() {};

var wm = new WeakMap();
wm.set(window, 'foo');
console.log(wm);/*w  ww  .j  a  v  a  2s . c om*/

let a = wm.has(window); // returns true
console.log(a);
a = wm.has('baz');  // returns false
console.log(a);



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