readline 对象的 Javascript 范围

Question

困惑为什么此代码在第二个提示后挂起:

var readline = require('readline');

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

function curry () {
  let inputs = []
  function _curry() {
    if (inputs.length > 5) {
      for (var i = 0; i < inputs.length; i++) {
        console.log(inputs[i]);
      }
    } else {
      rl.question("Number?", function(answer) {
        inputs.push(answer)
        rl.close();
        _curry()
      });
    }
  }
  _curry()
}

curry()

===>

~/Desktop$ node curry.js

Number?1

Number?2

HANG

但是，这个:

var readline = require('readline');

function curry () {
  let inputs = []
  function _curry() {
    if (inputs.length > 5) {
      for (var i = 0; i < inputs.length; i++) {
        console.log(inputs[i]);
      }
    } else {
      var rl = readline.createInterface({
        input: process.stdin,
        output: process.stdout
      });
      rl.question("Number?", function(answer) {
        inputs.push(answer)
        rl.close();
        _curry()
      });
    }
  }
  _curry()
}

curry()

工作正常:

数字？12号数量？3数量？4数量？5数量？6123456

这似乎是一个范围界定问题？阅读线没有关闭？吊装？

Answer 1

不，这与范围或声明提升无关。只是您太早关闭了 readline 实例(但它似乎是异步的，因此仍然显示第二个提示)。你应该使用

function curry () {
  // better don't use a global, especially if you don't leave it open
  const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout
  });
  let inputs = []
  function _curry() {
    if (inputs.length > 5) {
      rl.close(); // close it only once you're done with *everything*
      for (var i = 0; i < inputs.length; i++) {
        console.log(inputs[i]);
      }
    } else {
      rl.question("Number?", function(answer) {
        inputs.push(answer)
        _curry()
      });
    }
  }
  _curry()
}