Convert JavaScript string in dot notation into an object reference

Question

Given a JS object

var obj = { a: { b: \'1\', c: \'2\' } }

and a string

\"a.b\"

how can I convert the stri

Answer 1

Note if you're already using Lodash you can use the property or get functions:

var obj = { a: { b: '1', c: '2' } };
_.property('a.b')(obj); // => 1
_.get(obj, 'a.b'); // => 1

Underscore also has a property function but it doesn't support dot notation.

Answer 2

GET / SET answer that also works in react native (you can't assign to Object.prototype currently):

Object.defineProperty(Object.prototype, 'getNestedProp', {
    value: function(desc) {
        var obj = this;
        var arr = desc.split(".");
        while(arr.length && (obj = obj[arr.shift()]));
        return obj;
    },
    enumerable: false
});

Object.defineProperty(Object.prototype, 'setNestedProp', {
    value: function(desc, value) {
        var obj = this;
        var arr = desc.split(".");
        var last = arr.pop();
        while(arr.length && (obj = obj[arr.shift()]));
        obj[last] = value;
    },
    enumerable: false
});

Usage:

var a = { values: [{ value: null }] };
var b = { one: { two: 'foo' } };

a.setNestedProp('values.0.value', b.getNestedProp('one.two'));
console.log(a.values[0].value); // foo

Answer 3

You can obtain value of an object member by dot notation with a single line of code:

new Function('_', 'return _.' + path)(obj);

In you case:

var obj = { a: { b: '1', c: '2' } }
var val = new Function('_', 'return _.a.b')(obj);

To make it simple you may write a function like this:

function objGet(obj, path){
    return new Function('_', 'return _.' + path)(obj);
}

Explanation:

The Function constructor creates a new Function object. In JavaScript every function is actually a Function object. Syntax to create a function explicitly with Function constructor is:

new Function ([arg1[, arg2[, ...argN]],] functionBody)

where arguments(arg1 to argN) must be a string that corresponds to a valid javaScript identifier and functionBody is a string containing the javaScript statements comprising the function definition.

In our case we take the advantage of string function body to retrieve object member with dot notation.

Hope it helps.