Currently, I am creating a 3d array in js using the following:
var arr = [["name1", "place1", "data1"],
["name2", "place2", "data2"],
["name3", "place3", "data3"]];
I can access each element using arr[0] or arr[1]. But is there anyways I can access them using a key like this: arr["name1"] should give me the first one. Any suggestions? I think I am looking for a Hashmap like functionality.
The only way you could do that is by wrapping it in an object.
var arr = {
name1 : ["name1", "place1", "data1"],
name2 : ["name2", "place2", "data2"],
name3 : ["name3", "place3", "data3"]
};
The situation has changed in the six years since this question was asked.
Due to weak typing associative arrays can be faked in JavaScript:
>> var names = new Array();
undefined
>> names["first"] = "Dotan";
"Dotan"
>> names["last"] = "Cohen";
"Cohen"
>> for ( key in names ) { console.log(key+" "+names[key]) }
undefined
first Dotan
last Cohen
That is sometimes useful, and all browsers released since 2012 support it, but there are caveats! The array cannot be simply read back:
>> names
Array [ ]
More importantly, the array's length cannot be easily retrieved:
>> names.length
0
Therefore this is not an associative array in the sense that JavaScript would have supported it had it been intended, but rather a workaround that is often useful if for whatever reason a real JS object does not support what you need:
>> var names = {};
undefined
>> names.first = "Dotan";
"Dotan"
>> names.last = "Cohen";
"Cohen"
>> for ( key in names ) { console.log(key+" "+names[key]) }
undefined
first Dotan
last Cohen
>> names
Object { first: "Dotan", last: "Cohen" }
>> Object.keys(names).length
2
Javascript is a prototype based dynamic language. You can create objects and change their structure when you want.
var o = {name1: {place1: data1}, name2: {place2: data2}};
and access it with:
o.name1
The look-up implementation varies though and when you have a lot of properties that often changes this can be pretty slow (except in Chrome that uses a special scheme to access object properties i.e. embedded classes a-la-dynamic dispatch from smalltalk). Some libraries (e.g. MooTools) provide some hash map related structures,
o.name1.place1? and what would that give you? The value place1 or the value data1?