javascript object reference by array

Question

How can I refer to an object element dynamically during a loop by using an array, something like this:

var obj = {};
var lvl = ['x','y','z'];
var ol = [];
for (var l in lvl){
    ol.push( lvl[l] )
    obj[ol] = 'someval'
}

so where the reference may be obj[x][y][z] so each time the loop iterates, an additional key reference is appended, but I do not know how many levels there will be.

Not sure if I have explained that very well ?!

are you sure you want this? obj[ol] this will keep an array as key of object. or do you want obj[ol[l]]. — Mritunjay
– Mritunjay, Commented Jan 7, 2015 at 4:40
I am looking to dynamically add [] each time the loop iterates, so at the end of this example the refernce would be obj[x][y][z]. — crankshaft
– crankshaft, Commented Jan 7, 2015 at 4:42
Ok so just to be clear you want obj[x][y][z] = "someval". Essentially nesting object keys? — yoleg
– yoleg, Commented Jan 7, 2015 at 4:46
yes, I am looping through an array and I need to be able to push to or add key-value pairs to a nested object — crankshaft
– crankshaft, Commented Jan 7, 2015 at 4:48

yoleg · Accepted Answer · 2015-01-07 04:55:18Z

1

Based on how you answered my comment I believe this code will provide the nested object structure you are looking for.

var obj = {};
var lvl = ['x','y','z'];
var ol = {};

for (var i = 0; i < lvl.length; i++){
  obj[i] = {};  
  ol = obj[key];
}

answered Jan 7, 2015 at 4:55

yoleg

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2 Comments

slebetman Over a year ago

the var key in lvl bit is wrong because it would give you 0,1,2,length not x,y,z. Found out the hard way when testing my own answer. Use foreach or a regular for(x=0;x<lvl.length;x++) loop.

slebetman Over a year ago

Alternatively, you can change lvl to be {x:'',y:'',z:''} instead of an array.

slebetman · Accepted Answer · 2015-01-07 05:04:22Z

0

You mean you want someval to be the value of obj.x.y.z? You can always refer to the newly created levels using a variable:

var obj = {};
var levels = ['x','y','z'];

var pointer = obj;

for (var l=0; l<levels.length; l++) {
    key = levels[l];

    if (l < levels.length-1) {   // if not last element
        pointer[key] = {};
        pointer = pointer[key];
    }
    else {                       // if last element
        pointer[key] = 'someval';
    }
}

console.log(obj); // should log {x:{y:{z:"someval"}}}

edited Jan 7, 2015 at 5:04

answered Jan 7, 2015 at 4:48

slebetman

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1 Comment

slebetman Over a year ago

OK. Finally got it working. Remember, variables are references only when they're pointing to arrays or objects. But they're values once you assign a string or number to them.. arrrrgh...

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