How can I change order of items that are in .txt file in NodeJS using fs?
The items are one item = one line in .txt file.
I want to randomize/shuffle it and write shuffled version to the .txt file.
For a file with content as follows
first line
second
...
you can try something like this:
const fs = require('fs');
function shuffleArray(array) {
for (let i = array.length - 1; i > 0; i--) {
const j = Math.floor(Math.random() * (i + 1));
[array[i], array[j]] = [array[j], array[i]];
}
return array;
}
const array = fs.readFileSync('file.txt').toString().split("\n");
fs.writeFileSync('file.txt', shuffleArray(array).join('\n'));
Related
im trying to take an array and make it line by line, and write it in a new text file using writefilesync, for example: const arr = [1,2,3], in the text file it should show:
a
b
c
const fs = require ('fs');
const tip = [1,2,3]
for (let i =0; i < tip.length; i ++) {
tip[i] = tip[i] + "<br / >";
return tip;
}
let textFile = fs.writeFileSync ('text.txt', tip, 'utf8');
the result in the text file should be line by line
1
2
3
You are almost there, try with this one:
const fs = require ('fs');
const tip = [1,2,3];
const result = tip.join('\n');
let textFile = fs.writeFileSync ('text.txt', result, 'utf8');
Here, you are creating a string from the array by joining each element using a \n sign, which represents a newline.
The error in your code was that you were adding <br /> tag to break the lines, which is an HTML tag and it would work only in the browser but not in a regular file.
Using for-loop, the above would look like this:
const fs = require ('fs');
const tip = [1,2,3];
let result = '';
for (let i = 0; i < tip.length; i++) {
result += tip[i] + '\n';
}
let textFile = fs.writeFileSync ('text.txt', result, 'utf8');
I'm using Angular v4, i guess how can I build an Excel spreadsheet starting from an object in a component. I need to download the Excel file on the click of a button and I have to do this client side. I have a json file composed of arrays and I need to transfer this on an excel file, possibly customizable in style. Is it possible? If yes, how?
Edit:
No js libraries please, need to do this with Typescript and Angular
yourdata= jsonData
ConvertToCSV(objArray) {
var array = typeof objArray != 'object' ? JSON.parse(objArray) : objArray;
var str = '';
var row = "";
for (var index in objArray[0]) {
//Now convert each value to string and comma-separated
row += index + ',';
}
row = row.slice(0, -1);
//append Label row with line break
str += row + '\r\n';
for (var i = 0; i < array.length; i++) {
var line = '';
for (var index in array[i]) {
if (line != '') line += ','
line += array[i][index];
}
str += line + '\r\n';
}
return str;
}
in your html:
<button (click)="download()">export to excel</button>
in component:
download(){
var csvData = this.ConvertToCSV(yourdata);
var a = document.createElement("a");
a.setAttribute('style', 'display:none;');
document.body.appendChild(a);
var blob = new Blob([csvData], { type: 'text/csv' });
var url= window.URL.createObjectURL(blob);
a.href = url;
a.download = 'User_Results.csv';/* your file name*/
a.click();
return 'success';
}
Hope you it will help you
Vishwanath answer was working for me when i replaced "," with ";". In Typescript the implementation could look like this:
ConvertToCSV(objArray: any) {
const array = typeof objArray !== 'object' ? JSON.parse(objArray) : objArray;
let str = '';
let row = '';
for (const index of Object.keys(objArray[0])) {
row += `${index};`;
}
row = row.slice(0, -1);
str += `${row}\r\n`;
for (let i = 0; i < array.length; i++) {
let line = '';
for (const index of Object.keys(array[i])) {
if (line !== '') {
line += ';';
}
line += array[i][index];
}
str += `${line}\r\n`;
}
return str;
}
I hope this helps someone.
I think you will not get that done without js libraries in the background. What you need are the typings for utilizing it in your Angular project with typescript.
For creating an excel file you could use something like exceljs. To use it in your project also install the typings you can find here. I am not sure if this library fits... haven't used it before.
For downloading you should use FileSaver.js (I have already used it).
npm install file-saver --save
... and the typings:
npm install #types/file-saver --save-dev
For using FileSaver.js put the following import to your component:
import * as FileSaver from 'file-saver';
To trigger the download use that:
FileSaver.saveAs(fileData, "filename.xlsx")
'fileData' has to be a Blob.
Hope this helps a little.
it not is possible.
XLS is a binary format.
The project Apache POI(https://en.wikipedia.org/wiki/Apache_POI) name class as HSSF (Horrible SpreadSheet Format).
my recommendation, make it in server side.
I want to use Node.js to create a simple logging system which prints a line before the past line into a .txt file. However, I don't know how the file system functionality from Node.js works.
Can someone explain it?
Inserting data into the middle of a text file is not a simple task. If possible, you should append it to the end of your file.
The easiest way to append data some text file is to use build-in fs.appendFile(filename, data[, options], callback) function from fs module:
var fs = require('fs')
fs.appendFile('log.txt', 'new data', function (err) {
if (err) {
// append failed
} else {
// done
}
})
But if you want to write data to log file several times, then it'll be best to use fs.createWriteStream(path[, options]) function instead:
var fs = require('fs')
var logger = fs.createWriteStream('log.txt', {
flags: 'a' // 'a' means appending (old data will be preserved)
})
logger.write('some data') // append string to your file
logger.write('more data') // again
logger.write('and more') // again
Node will keep appending new data to your file every time you'll call .write, until your application will be closed, or until you'll manually close the stream calling .end:
logger.end() // close string
Note that logger.write in the above example does not write to a new line. To write data to a new line:
var writeLine = (line) => logger.write(`\n${line}`);
writeLine('Data written to a new line');
Simply use fs module and something like this:
fs.appendFile('server.log', 'string to append', function (err) {
if (err) return console.log(err);
console.log('Appended!');
});
Step 1
If you have a small file
Read all the file data in to memory
Step 2
Convert file data string into Array
Step 3
Search the array to find a location where you want to insert the text
Step 4
Once you have the location insert your text
yourArray.splice(index,0,"new added test");
Step 5
convert your array to string
yourArray.join("");
Step 6
write your file like so
fs.createWriteStream(yourArray);
This is not advised if your file is too big
I created a log file which prints data into text file using "Winston" logger. The source code is here below,
const { createLogger, format, transports } = require('winston');
var fs = require('fs')
var logger = fs.createWriteStream('Data Log.txt', {
flags: 'a'
})
const os = require('os');
var sleep = require('system-sleep');
var endOfLine = require('os').EOL;
var t = ' ';
var s = ' ';
var q = ' ';
var array1=[];
var array2=[];
var array3=[];
var array4=[];
array1[0] = 78;
array1[1] = 56;
array1[2] = 24;
array1[3] = 34;
for (var n=0;n<4;n++)
{
array2[n]=array1[n].toString();
}
for (var k=0;k<4;k++)
{
array3[k]=Buffer.from(' ');
}
for (var a=0;a<4;a++)
{
array4[a]=Buffer.from(array2[a]);
}
for (m=0;m<4;m++)
{
array4[m].copy(array3[m],0);
}
logger.write('Date'+q);
logger.write('Time'+(q+' '))
logger.write('Data 01'+t);
logger.write('Data 02'+t);
logger.write('Data 03'+t);
logger.write('Data 04'+t)
logger.write(endOfLine);
logger.write(endOfLine);
function mydata() //user defined function
{
logger.write(datechar+s);
logger.write(timechar+s);
for ( n = 0; n < 4; n++)
{
logger.write(array3[n]);
}
logger.write(endOfLine);
}
var now = new Date();
var dateFormat = require('dateformat');
var date = dateFormat(now,"isoDate");
var time = dateFormat(now, "h:MM:ss TT ");
var datechar = date.toString();
var timechar = time.toString();
mydata();
sleep(5*1000);
i have a folder stucture like
var/
testfolder1/
myfile.rb
data.rb
testfolder2/
home.rb
sub.rb
sample.rb
rute.rb
inside var folder contains subfolders(testfolder1,testfolder2) and some files(sample.rb,rute.rb)
in the following code returing a josn object that contains folders and files inside the var folder
like
{
'0': ['sample.rb', 'rute.rb'],
testfolder1: ['myfile.rb',
'data.rb',
],
testfolder2: ['home.rb',
'sub.rb',
]
}
code
var scriptsWithGroup = {};
fs.readdir('/home/var/', function(err, subfolder) {
if(err) return context.sendJson({}, 200);
var scripts = [];
for (var j = 0; j < subfolder.length; j++) {
var scriptsInFolder = [];
if(fs.lstatSync(scriptPath + subfolder[j]).isDirectory()) {
fs.readdirSync(scriptPath + subfolder[j]).forEach(function(file) {
if (file.substr(file.length - 3) == '.rb')
scriptsInFolder.push(file);
});
scriptsWithGroup[subfolder[j]] = scriptsInFolder;
} else {
if (subfolder[j].substr(subfolder[j].length - 3) == '.rb')
scripts.push(subfolder[j]);
}
}
scriptsWithGroup["0"] = scripts;
console.log(scriptsWithGroup)
context.sendJson(scriptsWithGroup, 200);
});
What i need is i want to return the latest modified or created files.here i only use 2 files inside folders it contains lots of files.so i want to return latest created ones
I'm going to assume here that you want only the most recent two files. If you actually want them all, just sorted, just remove the slice portion of this:
scriptsInFolder = scriptsInFolder.sort(function(a, b) {
// or mtime, if you're only wanting file changes and not file attribute changes
var time1 = fs.statSync(a).ctime;
var time2 = fs.statSync(b).ctime;
if (time1 < time2) return -1;
if (time1 > time2) return 1;
return 0;
}).slice(0, 2);
I'll add, however, that it's typically considered best practice not to use to the synchronize fs methods (e.g. fs.statSync). If you're able to install async, that would be a good alternative approach.
const fs = require('fs');
const path = require('path');
const getMostRecentFile = (dir) => {
const files = orderReccentFiles(dir);
return files.length ? files[0] : undefined;
};
const orderReccentFiles = (dir) => {
return fs.readdirSync(dir)
.filter(file => fs.lstatSync(path.join(dir, file)).isFile())
.map(file => ({ file, mtime: fs.lstatSync(path.join(dir, file)).mtime }))
.sort((a, b) => b.mtime.getTime() - a.mtime.getTime());
};
const dirPath = '<PATH>';
console.log(getMostRecentFile(dirPath));
I need to open an existing JavaScript file, check if this string exists:
var LocalStrategy = require('passport-local').Strategy;
If it doesn't, then append it at the top with the rest of require() lines.
In another case, I need to check if that string exists, and if it does, I would like to remove just that line.
I have looked at fs.readFile, fs.writeFile, fs.open but I don't think it is capable of doing what I need. Any suggestions?
This is a simplified script:
var fs = require('fs');
var search = "var LocalStrategy = require('passport-local').Strategy;";
function append (line) {
line = line || 0;
var body = fs.readFileSync('example.js').toString();
if (body.indexOf(search) < 0 ) {
body = body.split('\n');
body.splice(line + 1,0,search);
body = body.filter(function(str){ return str; }); // remove empty lines
var output = body.join('\n');
fs.writeFileSync('example.js', output);
}
}
function remove () {
var body = fs.readFileSync('example.js').toString();
var idx = body.indexOf(search);
if (idx >= 0 ) {
var output = body.substr(0, idx) + body.substr(idx + search.length);
fs.writeFileSync('example.js', output);
}
}