关于javascript的setinterval异步问题

Question

第一段代码

运行结果为正常

第二段代码

运行结果却和预期不一样

请问为什么会这样？？setInterval是异步执行的吗

Answer 1

var timer = nullvar a = [{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; index:1,&nbsp; &nbsp; &nbsp; &nbsp; },{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; index:10,&nbsp; &nbsp; &nbsp; &nbsp; },{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; index:20,&nbsp; &nbsp; &nbsp; &nbsp; },{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; index:30,&nbsp; &nbsp; &nbsp; &nbsp; },{&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; index:40,&nbsp; &nbsp; &nbsp; &nbsp; }]timer = setInterval(function(){&nbsp; &nbsp; &nbsp; &nbsp; for(var ll=0;ll<a.length;ll++){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; a[ll].index -= 1;&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; console.log( JSON.stringify( a ) )},3500);