JavaScript Checking if an element with the key exists


Example

To check if an element with a specified key exits in a WeakMap, use the .has() method. It returns true if it exits, and otherwise false.

const obj1 = {},
      obj2 = {};

const weakmap = new WeakMap([[obj1, 7]]);
console.log(weakmap.has(obj1)); // true
console.log(weakmap.has(obj2)); // false