I am trying to simply replace a line in a text file using JavaScript.
The idea is:
var oldLine = 'This is the old line';
var newLine = 'This new line replaces the old line';
Now i want to specify a file, find the oldLine and replace it with the newLine and save it.
Anyone who can help me here?
Just building on Shyam Tayal's answer, if you want to replace an entire line matching your string, and not just an exact matching string do the following instead:
fs.readFile(someFile, 'utf8', function(err, data) {
let searchString = 'to replace';
let re = new RegExp('^.*' + searchString + '.*$', 'gm');
let formatted = data.replace(re, 'a completely different line!');
fs.writeFile(someFile, formatted, 'utf8', function(err) {
if (err) return console.log(err);
});
});
The 'm' flag will treat the ^ and $ meta characters as the beginning and end of each line, not the beginning or end of the whole string.
So the above code would transform this txt file:
one line
a line to replace by something
third line
into this:
one line
a completely different line!
third line
This should do it
var fs = require('fs')
fs.readFile(someFile, 'utf8', function (err,data) {
var formatted = data.replace(/This is the old line/g, 'This new line replaces the old line');
fs.writeFile(someFile, formatted, 'utf8', function (err) {
if (err) return console.log(err);
});
});
