I am wondering if there is a simple way to get "synchronous" readline or at least get the appearance of synchronous I/O in node.js
I use something like this but it is quite awkward
var readline = require('readline');
var rl = readline.createInterface({
input: process.stdin,
output: process.stdout,
terminal: false
});
var i = 0;
var s1 = '';
var s2 = '';
rl.on('line', function(line){
if(i==0) { s1 = line; }
else if(i==1) { s2 = line; }
i++;
})
rl.on('close', function() {
//do something with lines
})'
Instead of this I would prefer if it were as easy as something like
var s1 = getline(); // or "await getline()?"
var s2 = getline(); // or "await getline()?"
Helpful conditions:
(a) Prefer not using external modules or /dev/stdio filehandle, I am submitting code to a code submission website and these do not work there
(b) Can use async/await or generators
(c) Should be line based
(d) Should not require reading entire stdin into memory before processing
Just in case someone stumbles upon here in future
Node11.7 added support for this doc_link using async await
const readline = require('readline');
//const fileStream = fs.createReadStream('input.txt');
const rl = readline.createInterface({
input: process.stdin, //or fileStream
output: process.stdout
});
for await (const line of rl) {
console.log(line)
}
Remember to wrap it in async function(){} otherwise you will get a reserved_keyword_error
const start = async () =>{
for await (const line of rl) {
console.log(line)
}
}
start()
To read an individual line, you can use the async iterator manually
const it = rl[Symbol.asyncIterator]();
const line1 = await it.next();
Like readline module, there is another module called readline-sync, which takes synchronous input.
const reader = require("readline-sync"); //npm install readline-sync
let username = reader.question("Username: ");
const password = reader.question("Password: ",{ hideEchoBack: true });
if (username == "admin" && password == "foobar") {
console.log("Welcome!")
}
You can just wrap it in a promise -
const answer = await new Promise(resolve => {
rl.question("What is your name? ", resolve)
})
console.log(answer)