Project-Canvas/UndoRedo.js at master · CHA0173/Project-Canvas · GitHub

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var newList = [];
var step = 0;


function saveHistory() {

  step++;

  lastStep = canvasReal.toDataURL();

  newList.push(lastStep);
}

$("#undo").click(function () {
  if (step > 0) {
    step--;
    let lastURL = newList[step - 1];
    let img = document.createElement('img');
    img.src = lastURL;
    img.onload = () => {
      contextReal.clearRect(0, 0, canvasReal.width, canvasReal.height);
      contextReal.drawImage(img, 0, 0);
    }
  }
})

$("#redo").click(function () {
  if (newList.length > step) {
    step++;
    let lastURL = newList[step - 1];
    let img = document.createElement('img');
    img.src = lastURL;
    img.onload = () => {
      contextReal.clearRect(0, 0, canvasReal.width, canvasReal.height);
      contextReal.drawImage(img, 0, 0);
    }

  }
})