How to create a hash or dictionary object in JavaScript

Question

I want to create a map object in javascript  I came to the following idea    var a   new Array     a  key1      value1    a  key2      value2     but then how I can find if a particular key exists or not

User · Accepted Answer

Don t use an array if you want named keys  use a plain object   var a       a  key1      value1   a  key2      value2     Then   if   key1  in a          something   else         something else

User · Answer

You want to create an Object  not an Array   Like so   var Map        Map  key1      value1   Map  key2      value2     You can check if the key exists in multiple ways   Map hasOwnProperty key   Map key     undefined    For illustration    Edit  remove null check if  key in Map

User · Answer

A built-in Map type is now available in JavaScript  It can be used instead of simply using Object  It is supported by current versions of all major browsers   Maps do not support the  subscript  notation used by Objects  That syntax implicitly casts the subscript value to a primitive string or symbol  Maps support any values as keys  so you must use the methods  get key    set key  value  and  has key     x000D   x000D  var m   new Map    x000D  var key1    key1   x000D  var key2       x000D  var key3       x000D   x000D  m set key1   value1    x000D  m set key2   value2    x000D   x000D  console assert m has key2    m should contain key2     x000D  console assert  m has key3    m should not contain key3     x000D   x000D   x000D    Objects only supports primitive strings and symbols as keys  because the values are stored as properties  If you were using Object  it wouldn t be able to to distinguish key2 and key3 because their string representations would be the same    x000D   x000D  var o   new Object    x000D  var key1    key1   x000D  var key2       x000D  var key3       x000D   x000D  o key1     value1   x000D  o key2     value2   x000D   x000D  console assert o hasOwnProperty key2    o should contain key2     x000D  console assert  o hasOwnProperty key3    o should not contain key3        Fails  x000D   x000D   x000D    Related   MDN Documentation  Map  Symbol  Set  WeakMap  WeakSet

User · Answer

Use the in operator  e g   key1  in a

User · Answer

if  a  desiredKey       undefined           it exists

[javascript] How to create a hash or dictionary object in JavaScript

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