Detailed explanation of the source code of JS mini game Speed ​​Run_javascript skills

/** 极速快跑
* Author: fdipzone
* Date: 2012-07-15
* Ver: 1.0
*/

var gameimg = ['images/start.png', 'images/start_over.png', 'images/go.png', 'images/go_over.png', 'images/running.gif', 'images/run_start1.gif', 'images/run_start2.gif', 'images/run_start3.gif'];
var speed_obj = new SpeedClass();

window.onload = function(){
 var callback = function(){
 speed_obj.init();
 }
 img_preload(gameimg, callback);
}

// Speed Class
function SpeedClass(){
 this.levelset = [8,5,8,12]; // 难度参数
 this.playerlist = null; // 选手列表
 this.player = 0;  // 选中的选手
 this.level = 2;  // 难度
 this.lock = 0;  // 锁定
 this.isstart = 0;  // 是否开始
 this.isover = 0;  // 是否结束
}

// init
SpeedClass.prototype.init = function(){
 this.reset();
 this.create_player();
 this.create_event();
}

// reset
SpeedClass.prototype.reset = function(){
 this.player = 0;
 this.level = $('level').value; // level
 this.playerlist = $_tag('li', 'playerlist');
 for(var i=0; i<this.playerlist.length; i++){
 this.playerlist[i].className = '';
 }
 disp('start_btn', 'show', 'start_btn');
 disp('go_btn', 'hide', 'go_btn');
 this.lock = 0; // unlock
 this.isstart = 0; // unstart
 this.isover = 0; // unover
}

// create player
SpeedClass.prototype.create_player = function(){
 var runway = [];
 var playerlist = [];
 for(var i=1; i<=8; i++){
 runway[i] = '<li><div id="player' + (9-i) + '" class="run_status1"></div></li>';
 playerlist[i] = '<li>' + i + '</li>';
 }
 $('runway').innerHTML = runway.join('');
 $('playerlist').innerHTML = playerlist.join('');
 runway = null;
 playerlist = null;
}

// create event
SpeedClass.prototype.create_event = function(){
 var self = this;
 this.playerlist = $_tag('li', 'playerlist');
 for(var i=0; i<this.playerlist.length; i++){
 this.playerlist[i].onmouseover = function(){
  if(this.className!='on'){
  this.className = 'over';
  }
 }
 this.playerlist[i].onmouseout = function(){
  if(this.className!='on'){
  this.className = '';
  }
 }
 this.playerlist[i].onclick = function(o,c){
  return function(){
  if(self.lock==0){
   o.playerlist[c].className = 'on';
   if(o.player!=0 && o.player!=c+1){ // 不等於0且不等於自己
   o.playerlist[o.player-1].className = '';
   }
   o.player = c + 1;
  }
  }
 }(self, i);
 }

 $('start_btn').onmouseover = function(){
 this.className = 'start_over_btn';
 }
 $('start_btn').onmouseout = function(){
 this.className = 'start_btn';
 }
 $('start_btn').onclick = function(){
 if(self.player==0){
  return alert('请选择要支持的选手');
 }else{
  self.lock = 1; // locked
  disp('start_btn','hide');
  disp('go_btn','show');
  for(var i=1; i<=8; i++){
  self.start(i);
  }
 }
 }

 $('go_btn').onmouseover = function(){
 this.className = 'go_over_btn'; 
 }
 $('go_btn').onmouseout = function(){
 this.className = 'go_btn';
 }
 $('go_btn').onclick = function(){
 self.go();
 }
}

// start game
SpeedClass.prototype.start = function(c){
 var o = $('player' + c);
 var step = 1;
 var self = this;
 var exert = 0;

 o.style.marginLeft = '62px'; // init
 
 var et = setInterval(function(){
 if(step<4){ // step 1-3 is ready
  o.className = 'run_status' + step;
 }else{
  // run
  if(o.className!='running'){
  o.className = 'running';
  }
  // start can go
  if(self.isstart==0){
  self.isstart = 1;
  }
  // 已有一名选手到达终点
  if(self.isover==1){
  clearInterval(et);
  }else{
  if(self.player!=c){ // 其他选手
   exert = Math.floor(Math.random()* self.levelset[self.level])+3; // 根据level调整
  }
  o.style.marginLeft = parseInt(o.style.marginLeft) + Math.floor(Math.random()*8)+4 + exert + 'px';
  // 到达终点
  if(parseInt(o.style.marginLeft)>=745){ 
   clearInterval(et);
   self.isover = 1;
   self.gameover(o.id);
  }
  }
 }
 step ++;
 }, 350)
}

// go
SpeedClass.prototype.go = function(){
 if(this.isstart==1 && this.isover==0){
 var o = $('player' + this.player);
 var exert = Math.floor(Math.random()*3)+2; // 2-5
 o.style.marginLeft = parseInt(o.style.marginLeft) + exert + 'px';
 }
 return false;
}

// gameover
SpeedClass.prototype.gameover = function(id){
 id = id.replace('player','');
 var self = this;
 var msg = '';
 if(id==this.player){
 msg = "恭喜你,你支持的选手获得胜利\n\n";
 }else{
 msg = "很遗憾,你支持的选手没有获得胜利,获胜的是" + id + "号选
\n";
 }
 if(confirm(msg + '是否重新开始&#63;')==true){
 setTimeout(function(){
  self.init();
 },1000);
 }else{
 return false;
 }
}

/** common function */

// get document.getElementBy(id)
function $(id){
 this.id = id;
 return document.getElementById(id);
}

// get document.getElementsByTagName
function $_tag(name, id){
 if(typeof(id)!='undefined'){
 return $(id).getElementsByTagName(name);
 }else{
 return document.getElementsByTagName(name); 
 }
}

/* div show and hide
* @param id dom id
* @param handle show or hide
* @param classname
*/
function disp(id, handle, classname){
 if(handle=='show'){
 $(id).style.display = 'block';
 }else{
 $(id).style.display = 'none'; 
 }
 if(typeof(classname)!='undefined'){
 $(id).className = classname;
 }
}

/* img preload
* @param img 要加载的图片数组
* @param callback 图片加载成功后回调方法
*/
function img_preload(img, callback){
 var onload_img = 0;
 var tmp_img = [];
 for(var i=0,imgnum=img.length; i<imgnum; i++){
 tmp_img[i] = new Image();
 tmp_img[i].src = img[i];
 if(tmp_img[i].complete){
  onload_img ++;
 }else{
  tmp_img[i].onload = function(){
  onload_img ++;
  }
 }
 }
 var et = setInterval(
 function(){
  if(onload_img==img.length){ // 定时器,判断图片完全加载后调用callback
  clearInterval(et);
  callback();
  }
 },200);
}