javascript - 如何将变量传递给函数并为其设置新值？

Question

我发现很难解释或搜索这个问题，所以我问 Stack Overflow。

我多次要求用户在终端中进行用户输入，并希望从中创建一个功能。接受问题和变量的函数，输入应添加到变量。

这是我的代码:

var name = 'hello',
    age = '11'

var readline = require('readline');
// var rl = readline.createInterface(process.stdin, process.stdout);
var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});
var getInput = function(inputVariable, question, cb) {
  rl.question(question, function(answer) {
    inputVariable = answer;
    rl.close();
    cb();
  });
}

var askForName = function() {
  console.log(1,age, name);
  getInput(name, "What's your name? ", askForAge);
}
var askForAge = function() {
  console.log(2,age, name);
  getInput(age, "How old are you? ", printIt);
}
var printIt = function() {
  console.log("Hello, " + name);
  console.log(".. and " + age + " old.");
}

askForName();

谢谢!

Answer 1

在 node.js 应用程序中，这通常使用回调链或 promise 来解决。

使用回调，您可以编写如下代码:

var getInput = function(question, cb) {
  rl.question(question, function(answer) {
    // Don't set the variable, but return value to callback
    rl.close();
    cb(answer);
  });
}

// ask* take a callback which they call with the value
var askForName = function(cb) {
  getInput("What's your name? ", cb);
}
var askForAge = function(cb) {
  getInput("How old are you? ", cb);
}
// printIt takes the values as parameters
var printIt = function(name, age) {
  console.log("Hello, " + name);
  console.log(".. and " + age + " old.");
}

// Now ask for name and age and store them as local variables
// inside callbacks
askForName(function(name) {
  askForAge(function(age) {
    printIt(name, age);
  });
});

我添加了评论来解释这些变化。基本上，值仅在回调之间传递，从不暴露给另一个范围。