javascript caesar密码算法 [英] javascript caesar cipher algorithm

问题描述

有没有做这个功能？，因为我觉得很难理解，特别是一个char参数表的功能，我不知道我在哪里或如何使用它。

Is there anyway to do this function?, because i find it quite difficult to understand, specially that function with a char parammeter which i dont see where or how i use it.

function trans(msg, rot) {
    //Reemplaza cada letra encontrada de la expresion [a-z], por el caracter codificado de la funcion
    return msg.replace(/([a-z])/ig,
        function(char) {
            var codASCII = char.charCodeAt(0);
            return String.fromCharCode( codASCII >= 97 ? (codASCII + rot + 26 - 97) % 26 + 97 : (codASCII + rot + 26 - 65) % 26 + 65 );
        });
}

提前谢谢你

推荐答案

让我们来看看 String.replace 的功能定义：

Let us have a look at String.replace's function definition:

str.replace(regexp|substr, newSubStr|function [, flags]);

在JavaScript中，我们可以将替换函数传递给 String.replace 函数。描述函数的参数如下所述：在本节的MDN文章。

In JavaScript, we can pass a replacement function to the String.replace function. How the arguments of the function is populated is described in this section of MDN article.

基本上：

• 第一个参数是与整个表达式匹配的字符串（相当于替换字符串中的 $& ）


• 随后的内容的捕获组（相当于 $ n 其中 n 是正数）。


• 跟随主要匹配的偏移量


• 最后一个参数是输入字符串

• The first argument is the string that matches the whole expression (equivalent to $& in replacement string)
• Followed by the content of the capturing groups (equivalent to $n where n is positive number). There will be as many arguments as the number of capturing groups.
• Followed by offset of the main match
• And the last argument is the input string.

所以与 /（[az]）/ ig 作为第一个参数（在这种情况下为 char ）提供给替换函数。匹配的字符将被替换。

So whatever matched by /([a-z])/ig will be supplied to the replacement function as the first argument (char in this case). The character matched will be processed and returned as the replacement.

在您的代码中， /（[az]）/ ig 可以简化为 / [az] / ig ，因为替换功能仅指主要匹配。

In your code, /([a-z])/ig can be simplified to /[a-z]/ig, since the replacement function only refers to the main match.

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