Constructors Back

1. Use class

• Always use class, and avoid manipulating prototype directly.

/**
 * bad
 */
function Queue(contents = []) {
    this._queue = [...contents];
}
Queue.prototype.pop = function () {
    const value = this._queue[0]
    this._queue.splice(0, 1);
    return value;
}

/**
 * good
 */
class Queue {
    constructor(contents = []) {
        this._queue = [...contents];
    }

    pop() {
        const value = this._queue[0];
        this._queue.splice(0, 1);
        return value;
    }
}

• name your class with the uppercase character.

/**
 * bad
 */
class puiManCheui {
}

/**
 * good
 */
class PuiManCheui {
}

2. Use extends for inheritance

the reason is that it's a built-in way to inherit prototype functionality without breaking instancof

/**
 * bad
 */
const inherits = require('inherits');
function PeekableQueue(contents) {
    Queue.apply(this, contents);
}
inherits(PeekableQueue, Queue);
PeekableQueue.prototype.peek = function () {
    return this._queue[0];
}

/**
 * good
 */
class PeekableQueue extends Queue {
    peek() {
        return this._queue[0];
    }
}

3. Use return this

• Methods can return this to help with method chaining.

/**
 * bad
 */
Aleen.prototype.jump = function () {
    this.jumping = true;
    return true;
}

Aleen.prototype.setHeight = function (height) {
    this.height = height;
}

const puiMan = new Aleen();
puiMan.jump();          /** => true         */
puiMan.setHeight(20);   /** => undefined    */

/**
 * good
 */
class Aleen {
    jump() {
        this.jumping = true;
        return this;
    }

    setHeight(height) {
        this.height = height;
        return this;
    }
}

const puiMan = new Aleen();
puiMan.jump()
    .setHeight(20);

4. toString()

• it's ok to write a custom toString() method, and you should make sure it works without any side effects.

class Aleen {
    constructor(options = {}) {
        this.name = options.name || 'no name';
    }

    getName() {
        return this.name;
    }

    toString() {
        return `Aleen - ${this.getName()}`;
    }
}