Getting the names of members of an array in javascript dynamically at runtime

Question

First of all I am not sure whether it is actually possible in javascript, but still I felt it's worth asking.

Ok, so what I am trying to do is get the names of the members of an array (or object as you might say) dynamically at runtime.

Let me explain. I have an object like this :

Results :-
member_name1 : value_1
member_name2 : value_2
member_name3 : value_3

Here, Result is the name of the object which has members like member_name1, member_name2, etc and theu have values like value_1 and value_2 respectively. What I am trying to do is get the name of the members like member_name1 this at runtime; not it's value. I access the value by Results.member_name1 generally.

I hope I am able to portray the issue!

Below is a screenshot of the object :

http://i.stack.imgur.com/dzAgm.png

Thanks!

Answer 1

Assuming obj is your object, you can get the names of all its properties this way:

var names = [];

for(var name in obj) {
    names.push(name);
}

However, be aware that this will also pick up any extensions that have been made to obj through the prototype property of its class. If you want to exclude these and only get the properties defined on obj itself, you can filter them out with

for(var name in obj) {
    if(obj.hasOwnProperty(name)) {
        names.push(name);
    }
}

More information on for...in on MDN.

Answer 2

You can access them using JavaScript for construct. Consider the following:

var member_names = [],
    data = {
        foo1: 'bar1',
        foo2: 'bar2',
        foo3: 'bar3',
    };

​for (var i in data) {
    member_names.push(i);
}

console.log(member_names);

​Here we have an empty array called *member_names* and your data object. In our loop, i will reference the property name, so you can push it onto the member_names array and then have access to them all there.