How can I pretty-print JSON using node.js?


Question

This seems like a solved problem but I am unable to find a solution for it.

Basically, I read a JSON file, change a key, and write back the new JSON to the same file. All works, but I loose the JSON formatting.So, instead of:

{
  name:'test',
  version:'1.0'
}

I get

{name:'test',version:'1.1'}

Is there a way in Node.js to write well formatted JSON to file ?

1
388
1/20/2016 1:12:29 AM

Accepted Answer

JSON.stringify's third parameter defines white-space insertion for pretty-printing. It can be a string or a number (number of spaces). Node can write to your filesystem with fs. Example:

var fs = require('fs');

fs.writeFile('test.json', JSON.stringify({ a:1, b:2, c:3 }, null, 4));
/* test.json:
{
     "a": 1,
     "b": 2,
     "c": 3,
}
*/

See the JSON.stringify() docs at MDN, Node fs docs

733
2/9/2017 11:43:11 PM

I think this might be useful... I love example code :)

var fs = require('fs');

var myData = {
  name:'test',
  version:'1.0'
}

var outputFilename = '/tmp/my.json';

fs.writeFile(outputFilename, JSON.stringify(myData, null, 4), function(err) {
    if(err) {
      console.log(err);
    } else {
      console.log("JSON saved to " + outputFilename);
    }
}); 

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