String2file.js

    function writeFile(content, name) {
      name =  name || 'filename.txt';
      var a = document.createElement('a');
      a.hidden = '';
      a.href = 'data:text/json,' + encodeURIComponent(content);
      a.download = name;
      a.textContent = 'Download file '+name+'!';
      console.log(a);
      document.body.appendChild(a);
    }
    
    writeFile('Hello world!', 'test');