Count a string(mixing English and Chinese characters) length, and this is a rough function.

strLen.js

/**
 * Description: Count a string (mixing English and Chinese characters) length. 
 *      A basic and rough function.
 * 
 * Performance:
 *      Multiple methods performance test on http://jsperf.com/count-string-length.
 *      You can see that using regexp to check range is very slow from the above test page.
 */
function strLen(str) {
    var count = 0;
    for (var i = 0, len = str.length; i < len; i++) {
        count += str.charCodeAt(i) < 256 ? 1 : 2;
    }
    return count;
}