javascript : Async/await in .replace

一个易于使用和理解的异步替换函数：

async function replaceAsync(str, regex, asyncFn) {
    const promises = [];
    str.replace(regex, (match, ...args) => {
        const promise = asyncFn(match, ...args);
        promises.push(promise);
    });
    const data = await Promise.all(promises);
    return str.replace(regex, () => data.shift());
}

它会执行两次替换功能，所以如果你要处理一些繁重的事情，请小心。不过，对于大多数用途来说，它非常方便。

这样使用：

replaceAsync(myString, /someregex/g, myAsyncFn)
    .then(replacedString => console.log(replacedString))

或者这个：

const replacedString = await replaceAsync(myString, /someregex/g, myAsyncFn);

不要忘记你的myAsyncFn必须返回一个承诺。

asyncFunction的一个例子：

async function myAsyncFn(match) {
    // match is an url for example.
    const fetchedJson = await fetch(match).then(r => r.json());
    return fetchedJson['date'];
}
function myAsyncFn(match) {
    // match is a file
    return new Promise((resolve, reject) => {
        fs.readFile(match, (err, data) => {
            if (err) return reject(err);
            resolve(data.toString())
        });
    });
}

本机replace方法不处理异步回调，您不能将它与返回promise的replacer一起使用。

然而，我们可以编写自己的replace函数来处理承诺：

async function(){
  return string.replace(regex, async (match)=>{
    let data = await someFunction(match)
    console.log(data); //gives correct data
    return data;
  })
}
function replaceAsync(str, re, callback) {
    // http://es5.github.io/#x15.5.4.11
    str = String(str);
    var parts = [],
        i = 0;
    if (Object.prototype.toString.call(re) == "[object RegExp]") {
        if (re.global)
            re.lastIndex = i;
        var m;
        while (m = re.exec(str)) {
            var args = m.concat([m.index, m.input]);
            parts.push(str.slice(i, m.index), callback.apply(null, args));
            i = re.lastIndex;
            if (!re.global)
                break; // for non-global regexes only take the first match
            if (m[0].length == 0)
                re.lastIndex++;
        }
    } else {
        re = String(re);
        i = str.indexOf(re);
        parts.push(str.slice(0, i), callback.apply(null, [re, i, str]));
        i += re.length;
    }
    parts.push(str.slice(i));
    return Promise.all(parts).then(function(strings) {
        return strings.join("");
    });
}

因此，不存在需要承诺的重载替换。所以只需重述您的代码：

async function(){
  let data = await someFunction();
  let output = string.replace(regex, data)
  return output;
}

当然，如果需要使用match值传递给异步函数，事情会变得有点复杂：

var sourceString = "sheepfoohelloworldgoocat";
var rx = /.o+/g;
var matches = [];
var mtch;
rx.lastIndex = 0; //play it safe... this regex might have state if it's reused
while((mtch = rx.exec(sourceString)) != null)
{
    //gather all of the matches up-front
    matches.push(mtch);
}
//now apply async function someFunction to each match
var promises = matches.map(m => someFunction(m));
//so we have an array of promises to wait for...
//you might prefer a loop with await in it so that
//you don't hit up your async resource with all
//these values in one big thrash...
var values = await Promise.all(promises);
//split the source string by the regex,
//so we have an array of the parts that weren't matched
var parts = sourceString.split(rx);
//now let's weave all the parts back together...
var outputArray = [];
outputArray.push(parts[0]);
values.forEach((v, i) => {
    outputArray.push(v);
    outputArray.push(parts[i + 1]);
});
//then join them back to a string... voila!
var result = outputArray.join("");

下面是Overcl9ck答案的改进版和更现代的版本：

async function replaceAsync(string, regexp, replacerFunction) {
    const replacements = await Promise.all(
        Array.from(string.matchAll(regexp),
            match => replacerFunction(...match)));
    let i = 0;
    return string.replace(regexp, () => replacements[i++]);
}

这需要一个更新的浏览器基线，因为String.prototype.matchAll在2019年全面推出（Edge除外，它在2020年初推出了基于Chromium的Edge）。但它至少同样简单，同时也更高效，只有第一次匹配，而不是创建一个无用的字符串，并且不会以昂贵的方式更改替换数组。

这是Overcl9ck在TypeScript:中实现的解决方案

const replaceAsync = async (str: string, regex: RegExp, asyncFn: (match: any, ...args: any) => Promise<any>) => {
    const promises: Promise<any>[] = []
    str.replace(regex, (match, ...args) => {
        promises.push(asyncFn(match, ...args))
        return match
    })
    const data = await Promise.all(promises)
    return str.replace(regex, () => data.shift())
}

还有另一个解决方案，这次是TypeScript。类似于Maxime的解决方案；语义上不寻常的"；初始replace()-在许多其他解决方案中使用match()进行调用。

async function replaceAsync(str: string, regex: RegExp, asyncFn: (match: string) => Promise<string>): Promise<string> {
  const promises = (str.match(regex) ?? []).map((match: string) => asyncFn(match));
  const data = await Promise.all(promises);
  return str.replace(regex, () => data.shift()!);
}

这里有一个使用递归函数的替代方法：

async function replaceAsync(str, regex, asyncFn) {
    const matches = str.match(regex);
    if (matches) {
        const replacement = await asyncFn(...matches);
        str = str.replace(matches[0], replacement);
        str = await replaceAsync(str, regex, asyncFn);
    }
    return str;
}