<script src="https://code.jquery.com/jquery-3.1.1.min.js"></script>
var a = 957.6;
var b = "1,570.80";
alert(parseFloat(b)); //j结果等于1
var bRes = b.replace(/,/g,''); //结果为 1570.80
if(parseFloat(a) > parseFloat(bRes)){
alert("a");
}else{
alert("b");
}