Replace multiple strings in a file using nodejs

Question

I have a json file in which I want to replace two words with two new words using fs of node js. I read the solution to a similar query on Replace a string in a file using nodejs. Then I tried the following code snippet but it replaces only a single word. I need to run it multiple times to replace multiple words.

Here is the code snippet:

var fs = require('fs')
fs.readFile('C:\\Data\\sr4_Intellij\\newman\\Collections\\api_collection.json', 'utf8', function (err,data) {
  if (err) {
    return console.log(err);
  }
  var result1 = data.replace(/{{Name}}/g, 'abc');
  var result2 = data.replace(/{{Address}}/g, 'xyz');
  var arr1 = [result1,result2]
  console.log(arr1[0]);

  fs.writeFile('C:\\Data\\sr4_Intellij\\newman\\Collections\\api_collection.json', arr1, 'utf8', function (err) {
     if (err) return console.log(err);
  });

});

javascript does not support recursive matching for regexp natively, maybe you want to use a library for that — FrontTheMachine
– FrontTheMachine, Commented Nov 7, 2017 at 9:13

T.J. Crowder · Accepted Answer · 2017-11-07 09:10:43Z

4

You need to do the second replace on the result of the first replace. data isn't changed by replace; replace returns a new string with the change.

So:

var result = data.replace(/{{Name}}/g, 'abc')
                 .replace(/{{Address}}/g, 'xyz');

...then write result to the file.

Alternately, and this particularly useful if it's a large file or you have lots of different things to replace, use a single replace with a callback:

var replacements = Object.assign(Object.create(null), {
    "{{Name}}": "abc",
    "{{Address}}": "xyz"
    // ...and so on...
});

var result = data.replace(/{{[^}]+}}/g, function(m) {
    return replacements[m] || m;
});

Or with a Map:

var replacements = new Map([
    ["{{Name}}", "abc"],
    ["{{Address}}", "xyz"]
    // ...and so on...
]);

var result = data.replace(/{{[^}]+}}/g, function(m) {
    return replacements.get(m) || m;
});

answered Nov 7, 2017 at 9:10

T.J. Crowder

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3 Comments

Saurav Rath Over a year ago

Hi Crowder, one more question: Can we replace these strings in multiple files at at a time ? Like writing into multiple files at a time. Thanks for your insights into this.

T.J. Crowder Over a year ago

@SauravRath: Not at the same time (unless you spawn child processes to do it), but you certainly can in a loop. Beware the closures in loops problem.

AMIC MING Over a year ago

nice solutions. Specifically I like that .replace.replace one. Thanks for the answer.

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