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I'm trying to read file.txt with some content like this:

jone
sia
alex
jad

and using node js I want to find the words that start with letter j
this is what I write:

let fs = require('fs');

fs.readFile('./file.txt', (err, info)=>
 let j;
 let con = 0;
 console.log(err)
 if(err) return;
 for (j=0; j < info.length; ++j)
 if (info[j] == 10)
 con++;
 console.log(con)
 if(info.indexOf('j') > -1)
 console.log(info.toString())
 
)

I want to print the number of lines in text file and the words that start with letter j
but the counter result is 3 while it should be 4 and it prints all info:

jone
sia
alex
jad

while it should print jone and jad only

how solve this

Here is your file.txt:

jone
sia
alex
jad

And here is the code:

const fs = require('fs');

const output = fs
 .readFileSync('file.txt', 'utf8')
 .trim()
 .split('n')
 .filter(word => word.includes('j'));

console.log(output);

This will get you everything that includes 'j'

If you want something that will start with j you can write your own filter function like so:

const fs = require('fs');

const output = fs
 .readFileSync('file.txt', 'utf8')
 .trim()
 .split('n');

function filter(names, index, letter) 
 return names.filter(word => word.charAt(index) === letter);


console.log('Length of originanl list: ', output.length);
console.log('Filtered List: ', filter(output, 0, 'j'));
console.log('Length of filtered list: ', filter(output, 0, 'j').length);

Live Demo Here

You can use the readline build in core module and do something like this:

var rl = require('readline'), fs = require('fs')

var lineReader = rl.createInterface( input: fs.createReadStream('file.txt') )

lineReader.on('line', function (name) 
 if(name.startsWith('j'))
 console.log(name)
)

See it working here

I suggest using the regular expressions approach.

info should be of type string, therefore it is possible for you to use the String.prototype function match(), like so:

let matches = info.match(expression);

or in your case: let matches = info.match(/bjw+/g); (example)

you can use regex to detect how many lines the text files has by detecting how many line breaks you have in your raw data (if possible):

let lines = info.match(/n/g).length + 1; (example)

All these answers are incredibly over-complicated.

Simply iterate through all words and check if it start with the letter:

for (const word of wordList.split("n")) 
 if (word.startsWith("j")) console.log(`$word start with the letter j`);