javascript计算字节数

javascript计算字节数：

function byteLength(s) {
var totalLength = 0;
	  	var charCode;
	  	for (var i = 0; i < s.length; ++i) {
	    	charCode = s.charCodeAt(i);
	    	if (charCode < 0x0080) {
	      		++totalLength;
	    	} else if (charCode < 0x0800) {
	      		totalLength += 2;
	    	} else if (charCode <= 0xffff) {
	      		totalLength += 3;
	    	} else {
	      		totalLength += 4;
	    	}
	  	}
	  	return totalLength;
}