var str ="Rome was not built in a day";
str=str.replace(/\s+/g,"");//去掉所有的空格
var sum =0;
for(var i of str)//for...of循环遍历字符串
{
sum++;
}
document.write("Rome was not built in a day有"+sum+"个字符串");
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<script>
</script>
</head>
<body>
</body>
</html>