Functions for working with objects.



merge(source, arguments)

Merges all of the properties of all arguments into the first argument. If two or more argument objects have properties with the same name, the property is overwritten with precedence from right to left, implying that properties of the object on the left are overwritten by a same named property of an object on the right. Properties are merged with descriptors onto the source object.

Any argument given with "falsy" values (null, undefined) in case of objects are skipped.

let { merge } = require("sdk/util/object");
var a = { jetpacks: "are yes", foo: 10 }
var b = merge(a, { foo: 5, bar: 6 }, { foo: 50, location: "SF" });

b === a    // true
b.jetpacks // "are yes"
b.foo      // 50
b.bar      // 6
b.location // "SF"

// Merge also translates property descriptors
var c = { "type": "addon" };
var d = {};
Object.defineProperty(d, "name", {
  value: "jetpacks",
  configurable: false
merge(c, d);
var props = Object.getOwnPropertyDescriptor(c, "name");
console.log(props.configurable); // true

source : object
The object that other properties are merged into.

arguments : object
n amount of additional objects that are merged into source object.


object : The source object.


Returns an object that inherits from the first argument and contains all of the properties from all following arguments, with precedence from right to left.

extend(source1, source2, source3) is the equivalent of merge(Object.create(source1), source2, source3).

let { extend } = require("sdk/util/object");
var a = { alpha: "a" };
var b = { beta: "b" };
var g = { gamma: "g", alpha: null };
var x = extend(a, b, g);

console.log(a); // { alpha: "a" }
console.log(b); // { beta: "b" }
console.log(g); // { gamma: "g", alpha: null }
console.log(x); // { alpha: null, beta: "b", gamma: "g" }

arguments : object
n arguments that get merged into a new object.


object : The new, merged object.

Document Tags and Contributors

Contributors to this page: wbamberg, jsantell
Last updated by: wbamberg,