获取字符串的字节长度

var str='我我我abc';
var bytesCount = 0;
for (var i = 0; i < str.length; i++)
{
    var c = str.charAt(i);
    if (/^[\u0000-\u00ff]$/.test(c)) //匹配单字节
    {
        bytesCount += 1;
        console.log(c);
    }
    else
    {
        bytesCount += 2;
    }
}