object-extend

A well-tested function to deep extend (or merge) JavaScript objects

object-extend

A well-tested function to deep extend (or merge) JavaScript objects without further dependencies.

Unit-tested with over 94 single assertion tests.

var a = {
    app: 'My App',
    environment: 'development',
    connections: {
        default: 'mysql',
        mysql: {
            driver: 'mysql',
            host: 'localhost',
            database: 'myapp.dev'
        }
    }
};
 
var b = {
    environment: 'production',
    connections: {
        mysql: {
            database: 'myapp.prod'
        }
    }
};
 
extend(a, b);
 
// Result: 
{
    app: 'My App',
    environment: 'production',
    connections: {
        default: 'mysql',
        mysql: {
            driver: 'mysql',
            host: 'localhost',
            database: 'myapp.prod'
        }
    }
}

Array: Only actual objects are extended. Arrays will not be merged but overwritten.

var a { foo: [1, 2, 3] };
var b { foo: [4, 5, 6] };
 
extend(a, b); // { foo: [4, 5, 6] } 

This function extends only enumerable properties without going up the prototype chain.

MIT.