处理 无效的 utf-16 编码

const replacement = '\ufffd';// https://gist.github.com/mathiasbynens/bbe7f870208abcfec860const loneSurrogates = /[\uD800-\uDBFF](?![\uDC00-\uDFFF])|([^\uD800-\uDBFF]|^)[\uDC00-\uDFFF]/g;// string sanitizes the given str by replacing invalid UTF-16 code unit// sequences with the unicode replacement character. Returns a new string.//用 \ufffd 取代无效的增补字节的，无效的高位或者低位exports.string = function(str) {    return str.replace(loneSurrogates, '$1' + replacement);}

原模块: https://github.com/felixge/node-unicode-sanitize/blob/master/index.js