CODEWITHSUNDEEP
javascriptarrays
eikood
eikood

Reputation: 13

JavaScript assoziativ array :/

what's the best way in JavaScript to store values in an assoziative array? I tried a lot of things and it always brakes somehow.

I tried something like:

var test = [];

for(var prop in json) {
     test[prop] = json[key];    
}

this works and i get a cool array then i can actually use. However calling test.length gives me 3 when there should be 10 items, it sometimes gives me 0 when there should be at least 8 items.

What do i do wrong? What's the best way to go here to get an assoziative array going which i can use properly like in Java?

Upvotes: 0

Views: 117

Answers (1)

Miloš Rašić
Miloš Rašić

Reputation: 2279

Everything is an object in JavaScript. foo['bar'] is the same as foo.bar. Array is just an object with some predefined methods that let it emulate what you would call a numeric array in PHP or just an array in almost any other language. JavaScript objects work like associative arrays in PHP. The general non-PHP name for it is hash.

So, to address your problem with length, it is a predefined property of an array object. Using it on an object that isn't an array will not give you the results you are expecting. To count the number of properties in an object, you can use

Object.keys(obj).length

in modern browsers. keys() function gets an array of keys from a hash, so it will have a correct length property.

If you wish to support older browsers, you have to iterate through object properties and count them manually. Be aware that for (var prop in json) will also iterate through the properties of every object in the prototype chain, so you might want to check if a property is object's own property using hasOwnProperty() method.

Upvotes: 3

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