How to set object property (of object property of..) given its string name in JavaScript?

function assign(obj, prop, value) {
    if (typeof prop === "string")
        prop = prop.split(".");

    if (prop.length > 1) {
        var e = prop.shift();
        assign(obj[e] =
                 Object.prototype.toString.call(obj[e]) === "[object Object]"
                 ? obj[e]
                 : {},
               prop,
               value);
    } else
        obj[prop[0]] = value;
}

var obj = {},
    propName = "foo.bar.foobar";

assign(obj, propName, "Value");

Since this question appears to be answered by incorrect answers, I'll just refer to the correct answer from a similar question

function setDeepValue(obj, value, path) {
    if (typeof path === "string") {
        var path = path.split('.');
    }

    if(path.length > 1){
        var p=path.shift();
        if(obj[p]==null || typeof obj[p]!== 'object'){
             obj[p] = {};
        }
        setDeepValue(obj[p], value, path);
    }else{
        obj[path[0]] = value;
    }
}

Use:

var obj = {};
setDeepValue(obj, 'Hello World', 'foo.bar.foobar');

I know it's an old one, but I see only custom functions in answers.
If you don't mind using a library, look at lodash _.set and _.get function.