How to build nested properties from key strings

Question

var keys1 = ["foo", "moreFoo"],
value1 = "bar",
keys2 = ["foo", "ultraFoo"],
value2 = "bigBar";

I'd like to make a function which would build me an object :

object {
foo : {moreFoo: "bar", ultraFoo: "bigBar"}
}

I thought of taking each one of my arrays and doing the following :

function recursiveObjectBuild(object, keys, value) {
    var index = 0;
    function loop(object, index) {
        var key = keys[index];
        //Property exists, go into it
        if (key in object) {
            loop(object[key], ++index);
        //Property doesn't exist, create it and go into it
        } else if (index < keys.length-1) {
            object[key] = {};
            loop(object[key], ++index);
        //At last key, set value
        } else {
            object[key] = value;
            return object;
        }
    }
    return loop(object, 0);
}

Which should work IMO but doesn't (infinite loop, must be a stupid mistake but can't see it).

And I'm sure there must be a much simpler way

Seems line#6 is an issue. i don't see where "object" gets set: " if (key in object) {". Also, why not use JSON in your object builder? — salah-1
– salah-1, Commented Jun 24, 2013 at 16:20
@mohamed-abshir object is received as a parameter by the recursive function How would you do it with JSON ? — Rayjax
– Rayjax, Commented Jun 24, 2013 at 16:49
@flav the array of keys is a nested set of keys. [foo, bar, foobar] means that i want to set the properties to Object.foo.bar.foobar Also, all those properties will be defined in the same object — Rayjax
– Rayjax, Commented Jun 24, 2013 at 16:50
Here is the Json syntax for the sample above: var JSONObject= { "foo":"bar", "moreFoo":"bigBar", "Altrafoo":bigBar }; — salah-1
– salah-1, Commented Jun 24, 2013 at 17:30

Andrew Clark · Accepted Answer · 2013-06-24 16:30:52Z

1

Try the following:

function objectBuild(object, keys, value) {
    for (var i = 0; i < keys.length-1; i++) {
        if (!object.hasOwnProperty(keys[i]))
            object[keys[i]] = {};
        object = object[keys[i]];
    }
    object[keys[keys.length-1]] = value;
}

Example usage (see it in action):

var object = {};
objectBuild(object, ["foo", "moreFoo"], "bar");
objectBuild(object, ["foo", "ultraFoo"], "bigBar");
// object --> {foo: {moreFoo: "bar", ultraFoo: "bigBar}}

edited Jun 24, 2013 at 16:30

answered Jun 24, 2013 at 16:24

Andrew Clark

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