JavaScript快速找出字符串并返回其下标

 var box = "this is javascript";
 for (var i = -1, arr = []; (i = box.indexOf("s", i + 1)) > -1;  arr.push(i));
 alert(arr); 

其原理还可以这样理解：

var str ="this is javascript"
var resault ={index:"",count:0};  

while ( true ){
  var  index =  str.indexOf("s") ;
  if(index == -1) break;
  resault.index += index +",";
  reaault.count++;
}  

resault.index = index.subString(0,resault.index.length-1);  

console.log("index:"+resault.index);
console.log("count:"+reaault.count);