javascript - JS 利用eval構建replace函數無效

問題描述

代碼含義：構建一個簡單的GADERYPOLUKI解碼器

The GADERYPOLUKI is a simple substitution cypher used in scouting to encrypt messages. The encryption is based on short, easy to remember key. The key is written as paired letters, which are in the cipher simple replacement.

example:

encode('ABCD', 'agedyropulik'); // => GBCE

代碼如下，我想用eval函數構建出可以替換字符的函數，但是貌似沒有用。

function decode(str,key) { key = key.split(’’) while (key.length>0) {let b = key.pop(), a = key.pop();eval(`str.replace(/${a}/g, '$')`)eval(`str.replace(/${a.toUpperCase()}/g, '${b.toUpperCase()}')`)eval(`str.replace(/$/g, '${a}')`)eval(`str.replace(/${b.toUpperCase()}/g, '${a.toUpperCase()}')`)console.log(a, b, str, `str.replace(/${a}/g, '$')`) } return str}console.log(decode('Hmdr nge brres', 'gaderypoluki'))console.log('Hmdr nge brres'.replace(/g/g, 'a'))>>> k i Hmdr nge brres str.replace(/k/g, 'i') l u Hmdr nge brres str.replace(/l/g, 'u') p o Hmdr nge brres str.replace(/p/g, 'o') r y Hmdr nge brres str.replace(/r/g, 'y') d e Hmdr nge brres str.replace(/d/g, 'e') g a Hmdr nge brres str.replace(/g/g, 'a') Hmdr nge brres Hmdr nae brres

問題解答

replace 不會改變原有值，而是返回新串。

其實你可以用 new RegExp(a, ’g’) 就不需要 eval