console 命令行工具 X clear
console
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charest="UTF-8"/>
        <title></title>
    </head>
    <body>
        <script>
            var str ="Rome was not built in a day";
            arr=str.replace(/\s/g,);
            var sum=0;
            for(var i of str)
            {
 
               sum++;

            }
            document.write(sum);
            </script>
    </body>
</html>