Create a download link for JSON file.

gistfile1.js

function makeJSONDownload(evt) {
  window.URL = window.URL || window.webkitURL;
  var content = JSON.stringify(p);
  var blob = new Blob([content], {type: 'application/json'});
  
  var link = document.createElement('a');
  link.href = window.URL.createObjectURL(blob);
  link.textContent = 'download here';
  link.download = 'test.json';
  document.getElementById('div').appendChild(link);
}
document.getElementById('btn').addEventListener('click', makeJSONDownload, false);