JS: Map.prototype.has

By Xah Lee. Date: . Last updated: .

New in ES2015.

map_obj.has(key)

Return true if key exist in map_obj. Else, false.

// check existence
const m = new Map([ [4, "n4"], [5, "n5"] ]);
console.log(m.has (5)); // true
console.log(m.has (99)); // false

Reference

ECMAScript 2015 §Keyed Collection#sec-map.prototype.has

JS Map Topic

  1. the Map Object Tutorial
  2. Map Object
  3. Map.prototype
  4. Iterate Over Map Object
  5. Convert Object to/from Map
  6. Map Filter
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