计算字符串长度, 中文算两个

count-string-length.js

function countStringLength (string) {
    var len = string.length;
    var count = 0;
    for (var i = 0; i < len; i ++) {
        var num = string.charCodeAt(i);
        if (num == 94 || num > 127) {
           count += 2;
        } else {
           count += 1;
        }
    }
    return count;
}

countStringLength('abc'); // => 3
countStringLength('abc啊'); // => 5

为什么有一个94呢