Add new properties of object in lodash

I believe you want to use the lodash merge function, rather than extend. See: Lodash - difference between .extend() / .assign() and .merge()

_.extend (now called _.assign) is indeed how you do this:

_.assign(a, b);

Live Example:

const a = {
    name: "value",
    name2: "value2",
};

const b = {
    name3: "value",
    name4: "value2",
};

_.assign(a, b);
console.log(JSON.stringify(a, null, 2));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.6/lodash.min.js"></script>

Though as of ES2015, you don't need Lodash for it, you can use the native Object.assign:

Live Example:

const a = {
    name: "value",
    name2: "value2",
};

const b = {
    name3: "value",
    name4: "value2",
};

Object.assign(a, b);
console.log(JSON.stringify(a, null, 2));

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.6/lodash.min.js"></script>

First of all, your defined objects are incorrect. Objects must be written as name:value pairs, separated by a colon (and not by an equality sign). Furthermore, you must use comma separators to delimit the properties of the object, like:

var person = {
    firstName: "Matthias",
    lastName: "Eckhart",
    eyeColor: "blue"
};

To extend an object with various properties via lodash, you can use _.assign(object, [sources], [customizer], [thisArg]):

var a = {
  name: "value",
  name2: "value2"
};

var b = {
  name3: "value",
  name4: "value2"
};

_.assign(a, b); // extend

console.log(a);

<script src="https://raw.githubusercontent.com/lodash/lodash/3.10.1/lodash.min.js"></script>