如何在nodejs中获取同步readline或使用异步“模拟”它？

Question

我想知道是否有一种简单的方法来获取“同步” readline或至少在node.js中获得同步I / O的外观

我用这样的东西，但是很尴尬

var readline = require('readline');
var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false
});

var i = 0;
var s1 = '';
var s2 = '';

rl.on('line', function(line){
    if(i==0) { s1 = line; }
    else if(i==1) { s2 = line; }
    i++;
})

rl.on('close', function() {
    //do something with lines
})'

取而代之的是，我希望它像这样简单

var s1 = getline(); // or "await getline()?"
var s2 = getline(); // or "await getline()?"

有用的条件：

（a）建议不要使用外部模块或/ dev / stdio文件句柄，我正在向代码提交网站提交代码，但这些代码在那儿不起作用

（b）可以使用异步/等待或生成器

（c）应基于行

（d）不需要在处理之前将整个标准输入读入内存

Answer 1

我认为这就是你想要的：

const readline = require('readline');

const rl = readline.createInterface({ input: process.stdin , output: process.stdout });

const getLine = (function () {
    const getLineGen = (async function* () {
        for await (const line of rl) {
            yield line;
        }
    })();
    return async () => ((await getLineGen.next()).value);
})();

const main = async () => {
    let a = Number(await getLine());
    let b = Number(await getLine());
    console.log(a+b);
    process.exit(0);
};

main();

注意：此答案使用实验性功能，需要 Node v11.7

Answer 2

万一将来有人偶然发现这里

Node11.7使用异步等待添加了对此doc_link的支持

const readline = require('readline');
//const fileStream = fs.createReadStream('input.txt');

const rl = readline.createInterface({
  input: process.stdin, //or fileStream 
  output: process.stdout
});

for await (const line of rl) {
  console.log(line)
}

请记住将其包装在异步函数中，否则您将得到reserver_keyword_error

Answer 3

尝试这个。它仍然不是同步行读取函数的完美复制——例如，async函数仍然稍后发生，所以你的一些调用代码可能会乱序执行，你不能从正常for循环内部调用它——但它很多比典型的.on或.question代码更容易阅读。

// standard 'readline' boilerplate
const readline = require('readline');
const readlineInterface = readline.createInterface({
        input: process.stdin,
        output: process.stdout
});

// new function that promises to ask a question and 
// resolve to its answer
function ask(questionText) {
  return new Promise((resolve, reject) => {
    readlineInterface.question(questionText, (input) => resolve(input) );
  });
}

// launch your program since `await` only works inside `async` functions
start()

// use promise-based `ask` function to ask several questions
// in a row and assign each answer to a variable
async function start() {
  console.log()
  let name = await ask("what is your name? ")
  let quest = await ask("what is your quest? ")
  let color = await ask("what is your favorite color? ")
  console.log("Hello " + name + "! " + 
    "Good luck with " + quest + 
    "and here is a " + color + " flower for you.");
  process.exit() 
}

更新：https : //www.npmjs.com/package/readline-promise实现它（源代码在这里：https : //github.com/bhoriuchi/readline-promise/blob/master/src/index.js#L192） . 它也实现了其他几个特性，但它们似乎也很有用，而且没有过度设计，不像其他一些 NPM 包声称做同样的事情。不幸的是，由于https://github.com/bhoriuchi/readline-promise/issues/5，我无法让它工作，但我喜欢它对中心功能的实现：

function ask(questionText) {
  return new Promise((resolve, reject) => {
    readlineInterface.question(questionText, resolve);
  });
}

Answer 4

你可以把它包装在一个承诺中 -

const answer = await new Promise(resolve => {
  rl.question("What is your name? ", resolve)
})
console.log(answer)

Answer 5

与readline模块一样，还有一个名为的模块readline-sync，它需要同步输入。

例：

const reader = require("readline-sync"); //npm install readline-sync
let username = reader.question("Username: ");
const password = reader.question("Password: ",{ hideEchoBack: true });
if (username == "admin" && password == "foobar") {
    console.log("Welcome!")
}

Answer 6

使用生成器，您的示例将如下所示：

var readline = require('readline');
var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false
});

var i = 0;
var s1 = '';
var s2 = '';

var iter=(function* () {
    s1 = yield;
    i++;
    s2 = yield;
    i++;
    while (true) {
        yield;
        i++;
    }
})(); iter.next();
rl.on('line', line=>iter.next(line))

rl.on('close', function() {
    //do something with lines
})

所以yield这里就像一个阻塞一样getline()，你可以以通常的顺序方式处理行。

UPD：
异步/等待版本可能如下所示：

var readline = require('readline');
var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout,
  terminal: false
});

var i = 0;
var s1 = '';
var s2 = '';

var continuation;
var getline = (() => {
    var thenable = {
        then: resolve => {
            continuation = resolve;
        }
    };
    return ()=>thenable;
})();
(async function() {
    s1 = await getline();
    i++;
    s2 = await getline();
    i++;
    while (true) {
        await getline();
        i++;
    }
})();
rl.on('line', line=>continuation(line))

rl.on('close', function() {
    //do something with lines
})

在这两个“同步”版本中，i不用于区分行，仅用于计算它们的总数。