How can I create HashMap in a JS file (in JQM)

Question

I am developing a mobile app using JQuery Mobile. Wanted to know whether can i create a HashMap the way we can do it in JAVA, in JQuery Mobile?

If yes, then how? please if possible provide me some example.

Answer 1

In plain Javascript it is possible to create something very similar to a java HashMap:

var hashmap = {};

Put something in it:

hashmap['key'] = 'value';

Get something out of it:

var value = hashmap['key'];

For most purposes this will do, but it is not exactly the same as a hashmap, see for example this question: JavaScript Hashmap Equivalent

Answer 2

Javascript (EcmaScript 5) currently only has Objects and Arrays. ES Harmony will introduce Maps and Sets, but that's quite a long way until it has wide enough support to effectively use it.

You can use an ordinary Object, in most cases it behaves like a Java-Hashmap.

// initialisation
var o = { key:"value", "another key", 3};
// or
var o = {};
o.key = "value";
// access property
alert(o.key);         // dot-notation
alert(o["key"]);      // bracket notation, same as array[i]
// delete property
delete o.key;

If the key is a valid identifier, you don't need to quote it and also can access it easily with dot-notation, if not (reserved keyword or spaces in it or ...), you need to quote it with either double or single quotes and address it with bracket notation.

Answer 3

An easy way to dynamically create a map in JavaScript is to use the following way.

I'm creating a map using an array which contains the id of html elements. In the end, I want to put the html elements ids and values in a key-value pair in a map.

var selectedFilterValuesMap = {};

for (var i = 0; i < filterIdArray.length; i++) {        
    selectedFilterValuesMap[filterIdArray[i].trim()] = $("#"+filterIdArray[i].trim()).val();
}

And, I can access the values in the map like this:

for(var x in selectedFilterValuesMap){
    alert("key - "+x+"\n val - "+selectedFilterValuesMap[x]);
}