Create a multidimensional array in javascript

Question

i'm not really sure, how to explain this, but i trying to create a multidimensional anonymes array in javascript. I'm new to Javascript and mostly did jQuery stuff so far. But now i need this and what i am trying to achieve should work like this somehow:

var
 outerArray = [],
 innerArray = new Array("position", "value", "done");
outerArray.push(innerArray);
// Then i want to use
outerArray["dynamicNameHere"]["position"] = 30;
outerArray["dynamicNameHere"]["value"] = 50;
outerArray["dynamicNameHere"]["done"] = false;
outerArray["otherDynamicNameHere"]["position"] = 100;
outerArray["otherDynamicNameHere"]["value"] = 500;
outerArray["otherDynamicNameHere"]["done"] = true;

The array is two-dimensional. Some values are booleans, but most of them are just integers as you can see in my example code. I hope my code help you understand my intention, because i'm not sure, how to explain it further. And, i know this code above doesn't work, but i have no idea, how to create something like this or if this is even possible with javascript (in PHP it is at least). This was just some code snippets i found about arrays and hoped this could work. But it didn't. But to me "push" seems like the way to do this?

Thanks for your help and time.

Answer 1

Arrays in JavaScript are for numerical indices only. There are no associative arrays.

You seem to want plain, nested objects:

outerObject = new Object();
outerObject["dynamicNameHere"] = new Object();
outerObject["dynamicNameHere"]["position"] = 30;
outerObject["dynamicNameHere"]["value"] = 50;
outerObject["dynamicNameHere"]["done"] = false;
outerObject["otherDynamicNameHere"] = new Object();
outerObject["otherDynamicNameHere"]["position"] = 100;
outerObject["otherDynamicNameHere"]["value"] = 500;
outerObject["otherDynamicNameHere"]["done"] = true;

But lots easier to use is the object literal notation:

var outerObject = {
 dynamicNameHere: {
 position: 30,
 value: 50,
 done: false
 },
 otherDynamicNameHere: {
 position: 100,
 value: 500,
 done: true
 }
}

Though, if those property names are really dynamic you will need to use the bracket notation for them:

var outerObject = {}, // empty object
 dynamicName = ...,
 otherDynamicName = ...;
outerObject[dynamicName] = {
 position: 30,
 value: 50,
 done: false
};
outerObject[otherDynamicName] = {
 position: 100,
 value: 500,
 done: true
};

• mrksbnch: Is there any way to check if a object with "dynamicNameHere" already exists?
• Bergi: You mean, whether a property with that name already exists on the outerObject?
• mrksbnch: Yes, something like if(!outerObject[dynamicName]) { /* Doesn't exist -> Create */ }. Because i need to somehow make sure that i am creating the object with "dynamicName" only once. Or doesn't that matter for javascript? At least in my code in need to change the values very often, basicly all the time if the users scrolls a page.
• Bergi: It doesn't matter, you could just overwrite it. But if you want to test it, you can use if( !(dynamicPropName in outerObject)) { /* doesn't exist */) which is a bit more reliable than checking for undefined.

Answer 2

It seems more, that you need an object and not an array:

var outerArray = {};
// add elements
outerArray[ 'dynamicNameHere' ] = {
 'position': 30,
 'value': 50,
 'done': false
};
// access those
console.log( outerArray[ 'dynamicNameHere' ][ 'position' ] );
// or
console.log( outerArray[ 'dynamicNameHere' ].position );