JavaScript - Language - The Secret Life of Objects(A Vector Type)

Eloquent JavaScript

開発環境

• OS X El Capitan - Apple (OS)
• Emacs (Text Editor)
• JavaScript (プログラミング言語)
• Node.js(JavaScript Engine)

Eloquent JavaScript(Marijn Haverbeke 著、No Starch Press)のPart 1(Language)、Chapter 6(The Secret Life of Objects)、Exercises(A Vector Type)を取り組んでみる。

Exercises(A Vector Type)

コード(Emacs)

'use strict';
var Vector,
    v1,
    v2;

Vector = function (x, y) {
    if (!(this instanceof Vector)) {
        return new Vector(x, y);
    }
    this.x = x;
    this.y = y;
};

Vector.prototype.plus = function (vect) {
    return new Vector(this.x + vect.x, this.y + vect.y);
};
Vector.prototype.minus = function (vect) {
    return new Vector(this.x - vect.x, this.y - vect.y);
};
Object.defineProperty(Vector.prototype, 'length', {
    get: function () {
        return Math.sqrt(Math.pow(this.x, 2) + Math.pow(this.y, 2));
    }
});

v1 = new Vector(1, 1);
v2 = new Vector(-1, 1);
console.log(v1, v2);
console.log(v1.plus(v2));
console.log(v1.minus(v2));
console.log(v1.length);
console.log(v2.length);

入出力結果(Terminal, Node.js)

$ node sample1.js
{ x: 1, y: 1 } { x: -1, y: 1 }
{ x: 0, y: 2 }
{ x: 2, y: 0 }
1.4142135623730951
1.4142135623730951
$