How to do associative array/hashing in JavaScript

javascript dictionary hashtable
George2 picture George2 · Jul 30, 2009 · Viewed 753.8k times · Source

I need to store some statistics using JavaScript in a way like I'd do it in C#: 

Dictionary<string, int> statistics;

statistics["Foo"] = 10;
statistics["Goo"] = statistics["Goo"] + 1;
statistics.Add("Zoo", 1);

Is there an Hashtable or something like Dictionary<TKey, TValue> in JavaScript?
How could I store values in such a way?

Answer

Alek Davis picture Alek Davis · Jul 30, 2009

Use JavaScript objects as associative arrays.

Associative Array: In simple words associative arrays use Strings instead of Integer numbers as index.

Create an object with

var dictionary = {};

JavaScript allows you to add properties to objects by using the following syntax:

Object.yourProperty = value;

An alternate syntax for the same is:

Object["yourProperty"] = value;

If you can, also create key-to-value object maps with the following syntax:

var point = { x:3, y:2 };

point["x"] // returns 3
point.y // returns 2

You can iterate through an associative array using the for..in loop construct as follows

for(var key in Object.keys(dict)){
  var value = dict[key];
  /* use key/value for intended purpose */
}

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