Node.js提示跳过输入

Question

I'm currently taking a course on Coursera, and doing an exercise using node.js code to calculate a quadratic expression. All the code is given and this exercise is merely to get us to know node.js, but still I'm encountering a problem entering a prompt.
the code is here:

var quad = require('./quadratic');

var prompt = require('prompt');

prompt.get(['a', 'b', 'c'], function (err, result) {
    if (err) { return onErr(err); }
    console.log('Command-line input received:');
    console.log('a: ' + result.a);
    console.log('b: ' + result.b);
    console.log('c: ' + result.c);

        quad(result.a,result.b,result.c, function(err,quadsolve) {
            if (err) {
                 console.log('Error: ', err);
                }
                else {
             console.log("Roots are "+quadsolve.root1() + "  " + quadsolve.root2());
                }
       });
});

As you see, I'm using the prompt module, but when I enter the input for a , the cmd is skipping the input for b and requesting me to enter `c, which in turn of couse, resulting in an error.

How to fix this issue, and why does it happen?

Answer 1

Welcome to developing on windows! Windows uses a carriage return in addition to a \\n line ending which is probably why you see this bug. You can force prompt to tokenize on a regular expression like this, which should hopefully fix your issue:

  var schema = {
    properties: {
      a: { pattern: /^[0-9]+$/, message: 'a', required: true },
      b: { pattern: /^[0-9]+$/, message: 'b', required: true },
      c: { pattern: /^[0-9]+$/, message: 'c', required: true }
    }
  };

  prompt.get(schema, function (err, result) {
      // .. rest of your code
  });