JavaScript Exercises

object.keys.js

Object.prototype.extendedValue = "extended";

var obj1 = {
	prop1: "value1",
	prop2: "value2"
};

var property;
for (property in obj1) {
	console.log(property + ":" + obj1[property]);
}

console.log("----");

var properties = Object.keys(obj1);
var i, len;
for (i = 0, len = properties.length; i < len; i++) {
	var property = properties[i];
	console.log(property + ":" + obj1[property]);
}

/*
prop1:value1
prop2:value2
extendedValue:extended
----
prop1:value1
prop2:value2
*/

prototype-ex1.js

// Not using prototype
function View(x, y) {
    this.x = x;
    this.y = y;
    this.redraw = function() {
        console.log("redraw at (" + this.x + "," + this.y + ")");
    };
}
var v1 = new View(1,2);
v1.redraw();
var v2 = new View(10,20);
v2.redraw();

v1.redraw !== v2.redraw && console.log("not same");

// Using prototype
function View2(x, y) {
    this.x = x;
    this.y = y;
}
View2.prototype.redraw = function() {
    console.log("redraw at (" + this.x + "," + this.y + ")");
};

var v3 = new View2(1,2);
v3.redraw();
var v4 = new View2(10,20);
v4.redraw();

v3.redraw === v4.redraw && console.log("same");


/*
redraw at (1,2)
redraw at (10,20)
not same
redraw at (1,2)
redraw at (10,20)
same
*/