Get JS object reference by multiple-level string value

Question

I'm not sure if it is possible to achieve such thing through JavaScript so I'm asking for help here.

I have a string:

var value = 'level1.level2.level3';

And I have an object:

var object = {
    level1 : {
        level2 : {
            level3 : 0
        },
    },
}

Is it possible to get a reference to that object using string value, not just value of specific object key. Using a traverse function but a reference so it could be possible to operate with it.

JSFiddle

I've checked and I'm sure this is NOT a duplicate question since in a duplicate version result of parsing function will be object key value, not the object key itself.

I'm afraid, you will have to write it

Maurice Perry
– Maurice Perry

2015-05-04 10:51:07 +00:00
Commented May 4, 2015 at 10:51 — Maurice Perry
– Maurice Perry, Commented May 4, 2015 at 10:51

Adassko · Accepted Answer · 2015-05-04 11:54:31Z

One liner:

[ob].concat(value.split('.')).reduce(function(a, b) { return a[b] })

Sample:

Object.prototype.getValue = function(path) {
    return [this].concat(path.split('.')).reduce(function(a, b) { return a[b] });
}

// usage:

alert((
{
    level1 : {
        level2 : {
           level3 : 0
        },
    },
}).getValue('level1.level2.level3'));

You cannot change the value of 0 in this way because it will be not an object reference

You need to get level1.level2 object and change its level3 field if you want to affect your original object

ob.getValue('level1.level2').level3 = 25;

- that's how javascript work

However, its possible to write a method to set its value

Object.prototype.setValue = function(path, value) {
    var last = (path = path.split('.')).splice(-1);
    [this].concat(path).reduce(function(a, b) { return a[b] })[last] = value;
}

var ob = {
  level1 : {
     level2 : {
       level3 : 0
     }
  }
};

ob.setValue('level1.level2.level3', 25);

alert(ob.level1.level2.level3);

Andrew Surzhynskyi · Accepted Answer · 2015-05-04 10:55:19Z

0

function getValue(object, path) {
    var array = path.split('.');
    var current = object;
    for (var i = 0; i < array.length; i++) {
        current = current[array[i]];
    }
    return current;
}

Use example var x = getValue(object, value);

answered May 4, 2015 at 10:55

Andrew Surzhynskyi

2,7761 gold badge25 silver badges32 bronze badges

Comments

Shalev Shalit · Accepted Answer · 2015-05-04 12:10:30Z

0

Although I hate using eval, you can try it if you absolutly sure about value:

var object = {
  level1 : {
     level2 : {
       level3 : 'text'
     }
  }
};

var value = 'level1.level2.level3';

$('.result').text(eval('object.' + value));

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class='result'></div>

answered May 4, 2015 at 12:10

Shalev Shalit

1,9634 gold badges24 silver badges34 bronze badges

1 Comment

Nimer Awad Over a year ago

it works, but the performance of eval is very bad!

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