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Arcade body.velocity.y returns NaN when extending Sprite


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Hi! I'm new to Phaser and have had great fun learning the engine. I recently started separating the code for my game into prefab files by extending Phaser.Sprite but I have run in to trouble. When Trying create the movement for the player I have a problem where the player starts moving randomly up or down on the y-scale. When inspecting my Player.prototype.update method in chrome I can see that this.body.velocity.y is NaN. I have no Idea how it got to be NaN pheraps some issue with the gravity? I have tried various fixes but I can't find the bug in my code. I have looked at numerous tutorials and they all look similar to what Im doing. Please help. Below is my code.


// Private
var leftKey;
var rightKey;
var jumpKey;
var speed = 150;
var jumpSpeed = 250;
// Constructor
function Player (game, x, y) {
  Phaser.Sprite.call(this, game, x, y, Player.key);
  this.body.bounce = 0;
  this.body.collideWorldBounds = true;
  this.body.allowGravity = true;

  leftKey = game.input.keyboard.addKey(Phaser.Keyboard.A);
  rightKey = game.input.keyboard.addKey(Phaser.Keyboard.D);
  jumpKey = game.input.keyboard.addKey(Phaser.Keyboard.SPACEBAR);

Player.prototype = Object.create(Phaser.Sprite.prototype);
Player.prototype.constructor = Player;

// Static
Player.preload = function(game) {
  game.load.image(Player.key, "images/block.png");
Player.key = "Player";

Player.prototype.update = function() {
  this.body.velocity.x = 0;

  if (leftKey.isDown) {
    this.body.velocity.x = -speed;
  } else if (rightKey.isDown) {
    this.body.velocity.x = speed;

  if (jumpKey.isDown && (this.body.onFloor() || this.body.touching.down)) {
    this.body.velocity.y = -jumpSpeed;

module.exports = Player;
var Player = require('../models/player.js');
var destiny = {};

/* The main game */
destiny.create = function () {
  console.info("Find out your destiny!");
  // World
  this.game.stage.backgroundColor = "#5599CC";
  this.game.world.setBounds(0, 0, 1000, 500);
  this.game.time.desiredFPS = 30;
  this.game.physics.arcade.gravity.y = 200;
  this.allSprites = {};

  // Player
  this.allSprites.destinyPlayer = new Player(this.game,2000,900);

  // Camera


destiny.update = function() {

destiny.render = function() {

module.exports = destiny;

My game is loaded in a series of game states (boot, preload, startscreen, preload, game). I have previously not had any problems with that part but if you want to see that code please ask.

Here is the error in chrome.


Any help is appreciated.

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I have tracked the setting of the NaN value to the preUpdate checkWorldBounds function. Here the following code exists in phaser 2.4.6

            pos.y = bounds.bottom - this.height;
            this.velocity.y *= -this.bounce.y;
            this.blocked.down = true;

It seems this.bounce.y has not been initiated to 0 but is undefined. I'm thinking that this is a bug? Any one else had this problem?

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On second thought I think the problem was me setting the sprites bounce value to 0 when initiating. I found this in some tutorial. When setting it to 0 that removes the point that was previously set and the x and y values are destroyed. I think a nan value here should cause an exception if possible so that its easier to debug this fault.

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