js获得文本框中值的字节长度

//获得输入框中字符长度
function getLength(val) {
	var str = new String(val);
	var bytesCount = 0;
	for (var i = 0 ,n = str.length; i < n; i++) {
		var c = str.charCodeAt(i);
		if ((c >= 0x0001 && c <= 0x007e) || (0xff60<=c && c<=0xff9f)) {
			bytesCount += 1;
		} else {
			bytesCount += 2;
		}
	}
	return bytesCount;
}