search a string in another file and replace it with another string in node js - regex

Question

I have searched enough for this matter and found most of the answers for java same problem but for me the problem arise in a node js program.
I want to search for,
.made-easy-theme{
color:black;
}
in a css file and replace its 'black' with another color which I recieve from the client side of the program. Here is what I have tried, I have tried 3 ways, but none of them are working.
First concept I have tried is,
var main = 'temp/' + userId + '/templates/' + appId + '/css/main.css';
var color = req.body.color;
function replaceThemecolor(color) {
fs.readFile(main, 'utf-8',
function (err, data) {
if (err) {
return console.log(err)
}
else {
var str = '.made-easy-theme{color:black;}';
if (str.search("black") != -1) {
var result = data.replace(/black/g, themecolor.color);
fs.writeFile(mainCss, result, 'utf-8', function (err) {
if (err) return console.log(err);
});
}
console.log(result);
}
});
}
});
The second concept I have tried is,
fs.readFile(main, 'utf-8',
function (err, data) {
if (err) {
return console.log(err)
}
else {
var ex = '.made-easy-theme{color:black;}'.includes('black');
if (ex == true) {
var result = data.replace(/black/g, color);
fs.writeFile(main, result, 'utf-8', function (err) {
if (err) return console.log(err);
});
console.log(result);
}
}
The third concept I have tried is,
else if (data.indexOf('.made-easy-theme{color:black;}') > 0) {
console.log(data);
var result = data.replace('black', themecolor.color);
fs.writeFile(mainCss, result, 'utf-8', function (err) {
if (err) return console.log(err);
});
};
Noone of these are working for me, please help to resolve this problem

Answer 1

I have found the answer
function replaceThemecolor(color) {
fs.readFile(main, 'utf-8',
function (err, data) {
var searchStr = ".made-easy-theme{color:black}";
var result = searchStr.replace(new RegExp('black', ''), color);
fs.writeFile(main, result, 'utf-8', function (err) {
if (err) return console.log(err);
});
});
}
but the problem is that it clears the full content of the css file and replace only the
.made-easy-theme{
color:black;
}
the other content which was in the css file is erased. I want to keep them and replce what I want to replace

Answer 2

Here is a way to do it, although not the best way. This code is coupled, makes bad use of string concatenation, doesn't do enough error checking and should probably use a file stream. But it will give you an idea.
Plus, it's just a dangerous thing to do.
var fs = require('fs');
var infile = 'test.css';
var outfile = 'temp.css';
var flag = false;
var color = 'green';
var out = '';
fs.open(infile, 'r', function(err, fd){
changeLine(fd);
});
function changeLine(fd){
var buf = new Buffer(1024);
buf.fill(0);
fs.read(fd, buf, 0, 1024, null, function(err, bytesRead, buffer){
if(bytesRead === 0){
writeCSS(out);
return;
}
var str = buffer.toString('utf8', 0, bytesRead);
if(/made-easy-theme/.exec(str)){
flag = true;
}
if (/color:/.exec(str) && flag){
str = str.replace('black', color);
flag = false;
}
out += str;
changeLine(fd);
});
}
function writeCSS(str){
fs.writeFile(outfile, str, function(err, written, buffer){
fs.rename(outfile, infile);
});
}