如何求出一个string中包含某个字符的个数

如何求出一个string中包含某个字符的个数

function strcountinstring(sourcestr,findstr) {
sourcestr=new String(sourcestr);
findstr=new String(findstr);
var findcount=0;
var startposition=0;

while (startposition searchstr=sourcestr.indexOf(findstr,startposition);
if (searchstr!=-1) {
findcount=findcount+1;
startposition=searchstr+findstr.length;
} else {
break;
}
}
return(findcount);
}