index.js

import Phaser from 'phaser'

export default class extends Phaser.Sprite {
    constructor( opts ){
        super( opts.game, opts.x || 0, opts.y || 0, opts.key || '', opts.frame || '' )

        // Enable player physics
        this.game.physics.enable( this, Phaser.Physics.ARCADE )

        // Player specifics
        this.body.collideWorldBounds = opts.hasOwnProperty('collideWorldBounds') ? opts.collideWorldBounds : true
        this.body.setSize( opts.width || 64, opts.height || 64 )
        this.health = opts.health || 1

        // Shortcut to current state object
        this.state = this.game.state.states[this.game.state.current]

        // Set up speed values
        this.speed = opts.speed || 350

        // Set up controls
        if( opts.hasOwnProperty('controls') ){
            this.cursors = this.game.input.keyboard.createCursorKeys()
        }

        // Set up diagonal movement dampener
        this.matchDiagonalSpeed =  opts.matchDiagonalSpeed || true

        // Shortcut to inverse of Pythagorean constant
        // (used to make diagonal speed match straight speed)
        this.pythInverse = 1 / Math.SQRT2
    }

    update(){
        // basic living/dying checks
        if( !this.alive ) return
        if( this.health <= 0 ){
            this.die()
        }

        // horizontal movement
        if( this.cursors.left.isDown ){
            this.body.velocity.x = -1
        } else if ( this.cursors.right.isDown ){
            this.body.velocity.x = 1
        } else {
            this.body.velocity.x = 0
        }

        // vertical movement
        if( this.cursors.up.isDown ){
            this.body.velocity.y = -1
        } else if ( this.cursors.down.isDown ){
            this.body.velocity.y = 1
        } else {
            this.body.velocity.y = 0
        }

        // If the player is moving diagonally, the resultant vector
        // will have a magnitude greather than the defined speed.
        // This section makes the magnitude of the player's movement
        // match the defined speed.
        let targetSpeed =
            (this.body.velocity.x != 0 && this.body.velocity.y != 0) ?
            this.speed * this.pythInverse :
            this.speed

        this.body.velocity.x *= targetSpeed
        this.body.velocity.y *= targetSpeed
    }
}