正则表达式捕获组JavaScript的字符串长度

如何解决正则表达式捕获组JavaScript的字符串长度

是否可以在JavaScript中获取正则表达式捕获组的字符串长度？我想用星号替换实际密码捕获组（即$ 2）的长度。

let urlRedacted = url.replace(/mongodb:\/\/(.+):(.+)@(.+)/,'mongodb://$1:*****@$3');

上面只是用硬编码的五个*****代替了密码（$ 2）的实际长度。

解决方法

使用回调函数将第二个组添加到变量中，然后.replace将所有*个组包含在该变量中：

const url = 'mongodb://foo:bar@baz';

const censor = str => str.replace(/./g,'*');
// could also do
// const censor = str => '*'.repeat(str.length);
let urlRedacted = url.replace(
  /mongodb:\/\/(.+):(.+)@(.+)/,(_,g1,g2,g3) => `mongodb://${g1}:${censor(g2)}@${g3}`
);

console.log(urlRedacted);

,

如果可以使用后视，则不需要 lambda：

const url = 'mongodb://foo:bar@baz';
let urlRedacted = url.replace(/(?<=mongodb:\/\/.+:[^@]*)[^@]/g,'*');
console.log(urlRedacted); // mongodb://foo:***@baz

见proof。

说明

--------------------------------------------------------------------------------
  (?<=                     look behind to see if there is:
--------------------------------------------------------------------------------
    mongodb:                 'mongodb:'
--------------------------------------------------------------------------------
    \/                       '/'
--------------------------------------------------------------------------------
    \/                       '/'
--------------------------------------------------------------------------------
    .+                       any character except \n (1 or more times
                             (matching the most amount possible))
--------------------------------------------------------------------------------
    :                        ':'
--------------------------------------------------------------------------------
    [^@]*                    any character except: '@' (0 or more
                             times (matching the most amount
                             possible))
--------------------------------------------------------------------------------
  )                        end of look-behind
--------------------------------------------------------------------------------
  [^@]                     any character except: '@'