javascript实现的简单计时器

//计时器window.timer = (function(){  function mod(opt){    //可配置参数 都带有默认值    //必选参数    this.ele = typeof(opt.ele)=='string'?document.getElementById(opt.ele):opt.ele;//元素    //可选参数    this.startT = opt.startT||0;//时间基数    this.endT = opt.endT=='undefined'?24*60*60:opt.endT;//结束时间 默认为一天    this.setStr = opt.setStr||null;//字符串拼接    this.countdown = opt.countdown||false;//倒计时    this.step = opt.step||1000;    //不可配置参数    this.timeV = this.startT;//当前时间    this.startB = false;//是否启动了计时    this.pauseB = false;//是否暂停    this.init();  }  mod.prototype = {    constructor : 'timer',    init : function(){      this.ele.innerHTML = this.setStr(this.timeV);    },    start : function(){      if(this.pauseB==true||this.startB == true){        this.pauseB = false;        return;      }      if(this.countdown==false&&this.endT<=this.cardinalNum){        return false;      }else if(this.countdown==true&&this.endT>=this.startT){        return false;      }      this.startB = true;      var v = this.startT,        this_ = this,        anim = null;      anim = setInterval(function(){        if(this_.startB==false||v==this_.endT){clearInterval(anim);return false}        if(this_.pauseB==true)return;        this_.timeV = this_.countdown?--v:++v;        this_.ele.innerHTML = this_.setStr(this_.timeV);      },this_.step);    },    reset : function(){      this.startB = false;      this.timeV = this.startT;      this.ele.innerHTML = this.setStr(this.timeV);    },    pause : function(){      if(this.startB == true)this.pauseB = true;    },    stop : function(){      this.startB = false;    }  }  return mod;})(); 

var timerO_1 = new timer({      ele : 'BOX1',      startT : 0,      endT : 15,      setStr : function(num){        return num+'s';      }    });var timerO_2 = new timer({      ele : 'BOX2',      startT : 30,      endT : 0,      countdown : true,      step : 500,      setStr : function(num){        return num+'s';      }    });