07-doc-get.js

/* PROXY */

const handleGet = (obj, prop) => {
  if (prop === "undo") {
    const last = obj.history.pop();

    if (!last) {
      return;
    }

    const { content, lastUpdated } = last;

    Reflect.set(obj, "content", content);
    Reflect.set(obj, "lastUpdated", lastUpdated);

    return { content, lastUpdated };
  }

  return Reflect.get(obj, prop);
};

const handleSet = (obj, prop, value) => {
  if (prop === "content" && value.length > 0 && value.length < 255) {
    const { content, lastUpdated, history = [] } = obj;
    const historyUpdated = [...history, { content, lastUpdated }];

    if (content && lastUpdated) {
      Reflect.set(obj, "history", historyUpdated);
    }
    Reflect.set(obj, prop, value);
    Reflect.set(obj, "lastUpdated", Date.now());

    return true;
  }

  console.error(
    "Content length should not be empty and be less than 255 characters"
  );

  return false;
};

const createDocProxy = (doc) => {
  return new Proxy(doc, {
    get: handleGet,
    set: handleSet
  });
};

/* INITIALIZE */

const doc = createDocProxy({
  content: "",
  lastUpdated: Date.now()
});

/* EVENTS */

const input = document.getElementById("data-input");

function save() {
  const value = input.value;
  doc.content = value;
}

function undo() {
  const previous = doc.undo;

  if (!previous) {
    return;
  }

  input.value = doc.content;
}