逐行节点 JS 提示输入不起作用

Question

我已经开始使用 node js 并且正在处理逐行依赖项。我已经逐行正确安装，它在文件夹中。目前，我的应用程序将运行但不会提示用户输入答案。我的代码如下：

var rlname;
var rlage;
var rlcolor;

// Create reading interface
const readline = require('readline');

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

// Ask a question
function getUserInput()
{
    rl.question("What is your name? \n", (name) => {
        console.log(name);
        rlname = name;
        // Log answer in JSON
    })

    rl.question("What is your age? \n", (age) => {
        console.log(age);
        rlage = age;
        // Log answer in JSON
    })

    rl.question("What is your favorite color? \n", (color) => {
        console.log(color);
        rlcolor = color;
        // Log answer in JSON
    })

    console.log("Hello " + rlname + ", you are " + rlage + " years old and your favorite color is " + rlcolor + ".");
}

getUserInput();
rl.close();

这是生成的结果：

What is your name?
Hello undefined, you are undefined years old and your favorite color is undefined.

Answer 1

这里的问题是 readline.question 是异步的，在您 (a) 可以使用输入和 (b) 创建下一个问题之前，您需要等待 return 的每个回调。但是，您正在 question 调用之后直接执行 console.log 语句。这可能是将 question 包装到承诺中的最简单方法，这样您就可以等待响应。

下面是一个使用 promises 的例子：

Answer 2

与 Node.js 中的许多模块一样，readline 以回调为基础工作。您传递给 rl.question 的回调函数不会立即运行；只有在收到用户的输入时才会调用它们。所以你的程序试图一次问三个问题，然后在收到任何答案之前立即记录你的“你好”行。（您可能没有看到第二个或第三个问题，因为 readline 为它们提供了一些内部缓冲区。）

使用回调，正确的做法是这样嵌套：

var rlname;
var rlage;
var rlcolor;

// Create reading interface
const readline = require('readline');

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

// Ask a question
function getUserInput()
{
    rl.question("What is your name? \n", (name) => {
        console.log(name);
        rlname = name;

        rl.question("What is your age? \n", (age) => {
            console.log(age);
            rlage = age;

            rl.question("What is your favorite color? \n", (color) => {
                console.log(color);
                rlcolor = color;

                console.log("Hello " + rlname + ", you are " + rlage + " years old and your favorite color is " + rlcolor + ".");

                rl.close();
            })
        })
    })
}

getUserInput();

（注意 rl.close 只有在所有问题都被问完后才能被调用，所以在最内层的回调中。）

使用带有 promises 的 async 函数会使这更容易理解，没有嵌套函数和深缩进。

Answer 3

这里的问题是因为这段代码本来应该是异步的，却写成同步的样子

更明确地说：您要求输入名称，但代码不等待输入，因为它是异步的。它继续向下到 console.log 语句并继续使用 rl.close().

关闭输入

你应该把每个问题都放在前一个回调中，最后一个回调中的结束语句：

var rlname;
var rlage;
var rlcolor;

// Create reading interface
const readline = require('readline');

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

// Ask a question
function getUserInput()
{
    // FIRST QUESTION
    rl.question("What is your name? \n", (name) => {
        console.log(name);
        rlname = name;
        
        // SECOND QUESTION
        rl.question("What is your age? \n", (age) => {
            console.log(age);
            rlage = age;
            
            // THIRD QUESTION
            rl.question("What is your favorite color? \n", (color) => {
                console.log(color);
                rlcolor = color;

                // LOG DATA
                console.log("Hello " + rlname + ", you are " + rlage + " years old and your favorite color is " + rlcolor + ".");
                
                // CLOSE CONNECTION
                rl.close();
            })
        })
    })
}

getUserInput();

逐行节点 JS 提示输入不起作用

Line-By-Line Node JS prompting for Input not functioning

javascript

user-input

node.js

line-by-line