在JavaScript中同时使用String Replace with Regex时如何获取捕获组的长度？

Question

I'm trying to achieve a simple Data Masking Function by replacing some parts of private data to asterisks(*) with javaScript string replace function.

So what I've done is as following:

  function privateDataMask(data, options) { var str = JSON.stringify(data); var i = 0, len = options.length; for (i; i < len; i++) { var opt = options[i]; var key = opt.key; var reg = opt.reg; var _reg = new RegExp('"' + key + '":"' + reg.source + '"', 'g'); //To get new reg which includes the key, like /"tel":"(\\d{3})(\\d*)(\\d{4})"/g str = str.replace(_reg, '"' + key + '":"$1*$3"'); //str = str.replace(_reg, '"' + key + '":"$1' + '*'.repeat($2.length) + '$3",'); //ReferenceError: $2 is not defined //str = str.replace(_reg, '"' + key + '":"$1' + '*'.repeat(RegExp.$2.length) + '$3",'); //https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp/n } return JSON.parse(str); } var data = [{ name: "王梅", tel: "15812346584", id: "22040219820418866X" }, { name: "吴青峰", tel: "13921345678", id: "450328197006157868" }, { name: "王张玉成", tel: "17734685988", id: "620100198109198020" } ]; var options = [{ key: 'name', reg: /([\一-\龥A-Za-z0-9\\·\\.]?)([\一-\龥A-Za-z0-9\\·\\.]+)([\一-\龥A-Za-z0-9\\·\\.]+)/ }, { key: 'tel', reg: /(\\d{3})(\\d*)(\\d{4})/ }, { key: 'id', reg: /(\\d{6})(\\d*)(\\d{5}(\\d|X){1})/ } ] var maskedData = privateDataMask(data, options); console.log(maskedData); 

It works somehow as expected, but still, I want to make little improvements, which can transfer for example, name: "吴青峰" -> name: "吴*峰", name: "王张玉成" -> name: "王**成", tel: "15812346584" -> tel: "158****6584", etc.

That is, adding multiple asterisks( ) to the parts replaced, and the number of asterisks( ) should equal to the length of captured group during String.replace().

As the commented lines indicate, I've tried things like '*'.repeat(RegExp.$2.length), the puzzle is RegExp.$n can only get value after the String.replace() function finishes, which leads to malposition.

Therefore, are there any methods to get the length of captured group concurrently during String.replace() function please ?

Answer 1

You can pass a function as second parameter to .replace() and that function will calculate the amount of * will be added.

_str = _str.replace(_reg, (text, start, middle, end) => `"${key}":"${start + '*'.repeat(middle.length) + end}"`);

Demo:

  function privateDataMask(data, options) { var str = JSON.stringify(data); var i = 0; var len = options.length; var _str, _data; for (i; i < len; i++) { var opt = options[i]; var key = opt.key; var reg = opt.reg; var _reg = new RegExp('"' + key + '":"' + reg.source + '"', 'g'); //To get new reg which includes the key, like /"tel":"(\\d{3})(\\d*)(\\d{4})"/g //console.log(_reg); if (!_str) { _str = str; } _str = _str.replace(_reg, (text, start, middle, end) => `"${key}":"${start + '*'.repeat(middle.length) + end}"`); } _data = JSON.parse(_str); return _data; } var data = [{ name: "王梅", tel: "15812346584", id: "22040219820418866X" }, { name: "吴青峰", tel: "13921345678", id: "450328197006157868" }, { name: "王张玉成", tel: "17734685988", id: "620100198109198020" } ]; var options = [{ key: 'name', reg: /([\一-\龥A-Za-z0-9\\·\\.]?)([\一-\龥A-Za-z0-9\\·\\.]+)([\一-\龥A-Za-z0-9\\·\\.]+)/ }, { key: 'tel', reg: /(\\d{3})(\\d*)(\\d{4})/ }, { key: 'id', reg: /(\\d{6})(\\d*)(\\d{5}(\\d|X){1})/ } ] var maskedData = privateDataMask(data, options); console.log(maskedData);