ejohn.org “Advanced JavaScript” Code Examples

learn.js

/* Chapter 14: Enforcing Function Context */

// http://ejohn.org/apps/learn/#86
Function.prototype.bind = function() {
    var fn = this, args = Array.prototype.slice.call(arguments), object = args.shift();
    return function() {
        return fn.apply(object, args.concat(Array.prototype.slice.call(arguments)));
    };
};
// function bind(context, name) {
//     return function() {
//         return context[name].apply(context, arguments);
//     };
// }
var Button = {
    click: function(value) {
        this.clicked = value;
    }
};
var elem = document.createElement("div");
elem.innerHTML = "Click me!";
elem.onclick = Button.click.bind(Button, true);
document.body.appendChild(elem);
elem.onclick();
console.log(Button.clicked);



/* Chapter 12: Inheritance */

// http://ejohn.org/apps/learn/#78
function Person() {}
Person.prototype.getName = function() {
	return this.name;
};
function Me() {
	this.name = "Manfred";
}
Me.prototype = new Person();
var me = new Me();
me.getName();



/* Chapter 9: Temporary Scope */

// http://ejohn.org/apps/learn/#62
var count = 0;
for(var i=0; i<4; i++) (function(i) {
    setTimeout(function() {
        console.log(i);
    }, i* 250);
})(i);



/* Chapter 8: Closures */

// http://ejohn.org/apps/learn/#52
var count = 0;
var timer = setInterval(function() {
    if(count <= 5) {
        console.log(count);
        count++;
    } else {
        clearInterval(timer);
    }
}, 250);

// http://ejohn.org/apps/learn/#53
var count = 1;
var elem = document.createElement("div");
elem.innerHTML = "Click Me!";
elem.onclick = function() {
	console.log(count++);
};
document.body.insertBefore(elem, document.body.firstChild);

// http://ejohn.org/apps/learn/#54
function Ninja() {
    var slices = 0;
    this.getSlices = function() {
        return slices;
    };
    this.slice = function() {
        slices++;
    }
}
var ninja = new Ninja();
ninja.slice();
ninja.getSlices() == 1;



/* Chapter 7: Flexible Arguments */

// http://ejohn.org/apps/learn/#40
function merge(root) {
	for(var i = 0; i < arguments.length; i++) {
		for(var key in arguments[i]) {
			root[key] = arguments[i][key];
		}
	}
	return root;
}

merge({a: 1}, {b: 2}, {c: 3, d: 4, e: 5});


// http://ejohn.org/apps/learn/#41
Array.prototype.min = function() {
	return Math.min.apply(Math, this);
}

Array.prototype.max = function() {
	return Math.max.apply(Math, this);
}

[222, 333, 111].min();
[222, 333, 111].max();


// http://ejohn.org/apps/learn/#45
function highest() {
	return Array.prototype.slice.call(arguments).sort(function(a, b) {
		return b - a;
	});
}

highest(99, 1111, 222)[0];


// http://ejohn.org/apps/learn/#46
function multiMax(multi) {
    var allButFirst = Array.prototype.slice.call(arguments, 1);
    var largestAllButFirst = Math.max.apply(Math, allButFirst);
    return multi * largestAllButFirst;
}

multiMax(3, 1, 2, 3);