Get readline input as an array

Question

I'm doing a programming challenge right now but I'm struggling with getting the input right. There is no feedback on my output, only "error" which makes it really hard to debug for me. Here is the input:

and I want to collect it like this:

[4, 2, 1, 4, 2, 9, 4, 7, 5, 8];

The test environment tells me to work with the input like this:

const readline = require('readline');

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

rl.on('line', (line) => {
    var nums = line.split(' ');
    /*Solve the test case and output the answer*/
});

How ever I must be getting the wrong array for my nums variable.I tried a bunch of approaches (splitting by /n and whitespaces, iterating with for loop and push... working with rl.close...) but as there is virtually no feedback on my input I am getting kind of desperate here. A simple interface which tells me my program output would help...

SOLUTION

var nums = [];
rl.on("line", line => {
  let newLine = line.split(" ");
  newLine.map(line => nums.push(line));
});

rl.on("close", function() {
console.log(nums)
});

It was possible for me to debug via the terminal once I got the input right.

Carr · Accepted Answer · 2020-03-03T08:50:49.120

The 'line' event would be emitted every time when rl read a new line, so you should just declare your nums outside of the callback function of the listener. Something like this:

...

var sums = [];

rl.on('line', (line) => {
    let newNumbers = line.split(' '); // [4, 2]
    sums.concat(newNumbers);
});

...

You may want to understand how event emitter and event listener work in JavaScript.

I think there is nothing for you even you register an 'error' event listener because everything is working as expected. And I believe there must be an event like 'end' or 'closed' which would be emitted after rl read all content of the input, and you can console.log your sums array there, I believe you can get your expected result.

You shouldn't handle the sums array right after the closing brackets, JavaScript is asynchronous, so those codes would be executed before all of the lines are read. If there is a method like rl.close you should call it in the situation like:

rl.on('line', (line) => {
 ...
 if (line === undefined) { // or any terminal character which createInterface would return. 
   rl.close();
 }
});

And I believe rl.close() will emit the event like what I said above , something like 'end' or 'closed', put the code to handle the final sums there.

Thanks for your reply. So after every `line` we run the function which splits that line and concats it into the global sums array. Do I put my code for working with the sums array right after the closing brackets of `rl.on`or do I have to use `rl.close`or something else for example? — marius, Mar 03 '20 at 08:41
Got it! It definitely helped to understand how the rl.input gets handled. It was possible for me to use the terminal, entering each line per hand and ending the input with `^c` The `close`event gets automatically fired after that, running the function as intended :) * I edited my original submission with the solution — marius, Mar 03 '20 at 09:42

score 0 · Answer 2 · answered Mar 03 '20 at 08:50

0

A simple interface which tells me my program output would help...

You can run your nodejs application with nodejs! You can download and install it, and then in your terminal node yourjscodefile.js. When you console.log(variable); it will output in the terminal.

answered Mar 03 '20 at 08:50

Roboroads

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Thanks for your input, I got it to work via the terminal after some trial and error on handling the `stdin`:) – marius Mar 03 '20 at 09:44

Get readline input as an array

2 Answers2