Mixin example in JS

mixin.js

// vastly simplified `mixin(..)` example:
function mixin( sourceObj, targetObj ) {
    for (var key in sourceObj) {
        // only copy if not already present
        if (!(key in targetObj)) {
            targetObj[key] = sourceObj[key];
        }
    }

    return targetObj;
}


var Engine = {
    engines: 1,
    ignition: function() {
        console.log( "Turning on my engine." );
    },
};



var SteeringWheel = {
    wheels: 1,

    drive: function() {
        this.ignition();
        console.log( "Steering and moving forward!" );
    }
};

var Car = mixin(Engine, {});
var Car = mixin(SteeringWheel, Car);



var Car = mixin( Car, {
    wheels: 4,

    drive: function() {
        SteeringWheel.drive.call( this );
        console.log( "Rolling on all " + this.wheels + " wheels!" );
    }
} );


c = Car;
console.log(c.wheels)
c.drive()