define-properties <sup>{rdoc-image:http://versionbadg.es/ljharb/define-properties.svg}[https://npmjs.org/package/define-properties]

Define multiple non-enumerable properties at once. Uses Object.defineProperty when available; falls back to standard assignment in older engines. Existing properties are not overridden. Accepts a map of property names to a predicate that, when true, force-overrides.

Example

var define = require('define-properties');
var assert = require('assert');

var obj = define({ a: 1, b: 2 }, {
        a: 10,
        b: 20,
        c: 30
});
assert(obj.a === 1);
assert(obj.b === 2);
assert(obj.c === 30);
if (define.supportsDescriptors) {
        assert.deepEqual(Object.keys(obj), ['a', 'b']);
        assert.deepEqual(Object.getOwnPropertyDescriptor(obj, 'c'), {
                configurable: true,
                enumerable: false,
                value: 30,
                writable: false
        });
}

Then, with predicates:

var define = require('define-properties');
var assert = require('assert');

var obj = define({ a: 1, b: 2, c: 3 }, {
        a: 10,
        b: 20,
        c: 30
}, {
        a: function () { return false; },
        b: function () { return true; }
});
assert(obj.a === 1);
assert(obj.b === 20);
assert(obj.c === 3);
if (define.supportsDescriptors) {
        assert.deepEqual(Object.keys(obj), ['a', 'c']);
        assert.deepEqual(Object.getOwnPropertyDescriptor(obj, 'b'), {
                configurable: true,
                enumerable: false,
                value: 20,
                writable: false
        });
}

Tests

Simply clone the repo, npm install, and run npm test