console.save

console-save.js

(function(console) {
  console.save = function(data, filename) {
    if (!data) {
      console.error("Console.save: No data");
      return;
    }

    if (!filename) filename = "console.json";

    if (typeof data === "object") {
      data = JSON.stringify(data, undefined, 4);
    }

    var blob = new Blob([data], { type: "text/json" }),
      e = document.createEvent("MouseEvents"),
      a = document.createElement("a");

    a.download = filename;
    a.href = window.URL.createObjectURL(blob);
    a.dataset.downloadurl = ["text/json", a.download, a.href].join(":");
    e.initMouseEvent("click", true, false, window, 0, 0, 0, 0, 0, false, false, false, false, 0, null);
    a.dispatchEvent(e);
  };
})(console);

https://stackoverflow.com/questions/11849562/how-to-save-the-output-of-a-console-logobject-to-a-file/19818659