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);