Extend a JavaScript object by passing a string with the path and a value

Question

Is there an easy way to extend a JavaScript object by passing a string and a value?

Basically I need something like this:

myObject = {}

var extendObj = function(obj, path, value){
}

var path = "a.b.c", value = "ciao";
extendObj(myObject, path, value);


console.log(myObject.a.b.c) //will print "ciao"

If they are undefined an empty object. If they are defined extend it. — Marco C
– Marco C, Commented Apr 24, 2013 at 2:03
It IS ambiguous, but I am guessing the assumption would be - if it does not exist already, create it as an object. I think the real ambiguity here lies in this: what should it do if b already exists, but is a number and therefore cannot have a string as member. — Chris O'Kelly
– Chris O'Kelly, Commented Apr 24, 2013 at 2:04
From "javascript dynamic object path", see stackoverflow.com/questions/2061325/… , stackoverflow.com/questions/6491463/… , stackoverflow.com/questions/13719593/… , etc. — user2246674
– user2246674, Commented Apr 24, 2013 at 2:06
@Chris "what should it do if b already exists, but is a number and therefore cannot have a string as member" this case will not appen — Marco C
– Marco C, Commented Apr 24, 2013 at 2:09

Derek 朕會功夫 · Accepted Answer · 2013-04-24 03:09:14Z

3

myObject = {};

var extendObj = function (obj, path, value) {
    var levels = path.split("."),
        i = 0;

    function createLevel(child) {
        var name = levels[i++];
        if(typeof child[name] !== "undefined" && child[name] !== null) {
            if(typeof child[name] !== "object" && typeof child[name] !== "function") {
                console.warn("Rewriting " + name);
                child[name] = {};
            }
        } else {
            child[name] = {};
        }
        if(i == levels.length) {
            child[name] = value;
        } else {
            createLevel(child[name]);
        }
    }
    createLevel(obj);
    return obj;
}

var path = "a.b.c",
    value = "ciao";
extendObj(myObject, path, value);


console.log(myObject.a.b.c) //will print "ciao"

http://jsfiddle.net/DerekL/AKB4Q/

enter image description here

You can see in the console that it creates the path according to path you entered.

edited Apr 24, 2013 at 3:09

answered Apr 24, 2013 at 2:07

Derek 朕會功夫

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2 Comments

Derek 朕會功夫 Over a year ago

@MarcoCalì - I have tweaked the code a little bit so that it will: 1. preserve values that already exist in the object and, 2. rewrite the property if the type of the existing value is not an object.

bfavaretto Over a year ago

+1 Clever use of recursion! Just a few details: <strike>you don't have to pass value when you recurse (you never use arguments[1] indeed);</strike> you don't have to rewrite functions, as they can have properties; it will fail if a or b is null (typeof null === "object").

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