How do I save JSON to local text file

Here is a solution on pure js. You can do it with html5 saveAs. For example this lib could be helpful: https://github.com/eligrey/FileSaver.js
Look at the demo: http://eligrey.com/demos/FileSaver.js/
P.S. There is no information about json save, but you can do it changing file type to "application/json" and format to .json

import { saveAs } from 'file-saver'

let data = { a: 'aaa' , b: 'bbb' }

let blob = new Blob([JSON.stringify(data)], { type: 'application/json' })
    
saveAs(blob, 'export.json')

Node.js:

var fs = require('fs');
fs.writeFile("test.txt", jsonData, function(err) {
    if (err) {
        console.log(err);
    }
});

Browser (webapi):

function download(content, fileName, contentType) {
    var a = document.createElement("a");
    var file = new Blob([content], {type: contentType});
    a.href = URL.createObjectURL(file);
    a.download = fileName;
    a.click();
}
download(jsonData, 'json.txt', 'text/plain');

It's my solution to save local data to txt file.

function export2txt() {
  const originalData = {
    members: [{
        name: "cliff",
        age: "34"
      },
      {
        name: "ted",
        age: "42"
      },
      {
        name: "bob",
        age: "12"
      }
    ]
  };

  const a = document.createElement("a");
  a.href = URL.createObjectURL(new Blob([JSON.stringify(originalData, null, 2)], {
    type: "text/plain"
  }));
  a.setAttribute("download", "data.txt");
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
}

<button onclick="export2txt()">Export data to local txt file</button>