var marginLeft = parseInt(ball.style.marginLeft, 10) style为null
var ball1=document.querySelector('ball-1');
var ball2=document.querySelector('ball-2');
var ball3=document.querySelector('ball-3');
var Promise = window.Promise;
function promiseAnimate(ball, distane){
return new Promise(function(resolve, reject){
function _animate(){
setTimeout(function(){
var marginLeft = parseInt(ball.style.marginLeft, 10)
if (marginLeft===distane) {
resolve()
} else{
if(marginLeft < distane){
marginLeft++
} else{
marginLeft--
}
ball.style.marginLeft = marginLeft + 'px'
_animate()
}
},13)
}
_animate()
})
}
promiseAnimate(ball1, 100)
.then(function(){
return promiseAnimate(ball2, 200)
})
.then(function(){
return promiseAnimate(ball3, 300)
})
.then(function(){
return promiseAnimate(ball3, 150)
})
.then(function(){
return promiseAnimate(ball2, 150)
})
.then(function(){
return promiseAnimate(ball1, 150)
})
