Add multiple attributes to an existing js object

In ES6/ ES2015 you can use the Object.assign method

let obj = {key1: true};
console.log('old obj: ', obj);
let newObj = {key2: false, key3: false};

Object.assign(obj, newObj);
console.log('modified obj: ', obj);


From How can I merge properties of two JavaScript objects dynamically?

var obj2 = {name: 'don', gender: 'male'};
for (var attrname in myobject) { myobject[attrname] = obj2[attrname]; }

EDIT

To be a bit clearer about how you could extend Object to use this function:

//Extend the protype so you can make calls on the instance
Object.prototype.merge = function(obj2) {
    for (var attrname in obj2) {
        this[attrname] = obj2[attrname];
    }
    //Returning this is optional and certainly up to your implementation.  
    //It allows for nice method chaining.
    return this;
};
//Append to the object constructor function so you can only make static calls
Object.merge2 = function(obj1, obj2) {
    for (var attrname in obj2) {
        obj1[attrname] = obj2[attrname];
    }
    //Returning obj1 is optional and certainly up to your implementation
    return obj1;
};

Usage:

var myObject1 = { One: "One" };
myObject1.merge({ Two: "Two" }).merge({ Three: "Three" });
//myObject1 is { One: "One", Two: "Two", Three: "Three", merge: function }


var myObject2 = Object.merge2({ One: "One" }, { Two: "Two" });
Object.merge2(myObject2, { Three: "Three" });
//myObject2 is { One: "One", Two: "Two", Three: "Three" }

Note: You certainly could implement a flexible merge conflict strategy depending on your needs.


I'm not sure if that's helpful, but there is a trick using JS ES6 spread syntax:

let obj = {a: 1, b: 2};
obj = {...obj, b: 3, c: 4};
console.log(obj); // {a: 1, b: 3, c: 4}

You can try to use this somehow... In general, that's a single liner to add or override object properties using js destructuring method.

Edit: Notice that the placement of ...obj in the new object is cruicial, as placing it first would allow overriding it with the following params (b: 3, c: 4 in my example), and placing it last will give priority to the members that are already in the object.