I want to use nodejs to read a file line by line and then when it finishes get the returned result as a json string. I was trying to do like this, but at the end the console.log prints undefined and not the list. I got the list and the end of the promise but how do I return it to the calling function in main.js?
I have my main.js file:
var fct = require('./romlist-parser');
console.log(fct.myfunction());
and the romlist-parser.js has the following content:
var fs = require('fs');
var readline = require('readline');
exports.myfunction = function() {
var promise = new Promise(function(resolve,reject) {
var rd = readline.createInterface({
input: fs.createReadStream('Atari 2600.txt'),
console: false
});
var games = [];
rd.on('line', function(line) {
var arr = line.split(";");
games.push({name:arr[0], title:arr[1]});
});
rd.on('close', function() {
var json = JSON.stringify(games);
resolve(games);
});
});
promise.then((resolveResult) => {
console.log(resolveResult);
return resolveResult;
});
};
Try this:
exports.myfunction = function() {
var promise = new Promise(function(resolve,reject) {
var games = [];
var rl = readline('./Atari 2600.txt'); // provide correct file path
rl.on('line', function (line, lineCount, byteCount) {
// console.log(lineCount, line, byteCount);
var arr = line.split(";");
games.push({name:arr[0], title:arr[1]});
})
.on('close', function() {
var json = JSON.stringify(games);
resolve(games); // resolve(json); may be??
})
.on('error', function (e) {
console.log("error", e);
// something went wrong
});
});
promise.then((resolveResult) => {
console.log(resolveResult);
return resolveResult;
});
};
P.S. This code can be improved further but for sake of simplicity and your understanding answer is limited to the style/code posted in the post. Else it can vary style to style.