The Document.mozSetImageElement() method changes the element being used as the CSS background for a background with a given background element ID.

• imageElementId is a string indicating the name of an element that has been specified as a background image using the -moz-element CSS function.
• imageElement is the new element to use as the background corresponding to that image element string. Specify null to remove the background element.

None (undefined).

This example changes the background of a <div> block each time the block is clicked by the user.

View this example live.

<style>
  #mybox {
    background-image: -moz-element(#canvasbg);
    text-align: center;
    width: 400px;
    height: 400px;
    cursor: pointer;
  }
</style>

The CSS defined by the <style> block above is used by our <div> to use an element with the id "canvasbg" as its background.

let c = 0x00;
function clicked() {
  const canvas = document.createElement("canvas");
  canvas.setAttribute("width", 100);
  canvas.setAttribute("height", 100);

  const ctx = canvas.getContext("2d");
  ctx.fillStyle = `#${c.toString(16)}0000`;
  ctx.fillRect(25, 25, 75, 75);

  c += 0x11;
  if (c > 0xff) {
    c = 0x00;
  }

  document.mozSetImageElement("canvasbg", canvas);
}

The code here is called each time the user clicks the <div> element. It creates a new <canvas> with the width and height set to 100 pixels, then draws into it a 50 by 50 pixel square. Each time the function is called, the square is a different color (its red component is increased each time), so each time the user clicks the element, the background is filled with a brighter and brighter pattern of red tiles.

Once the canvas is drawn, document.mozSetImageElement() is called to set the background for any CSS using the ID "canvasbg" as its background element ID to be our new canvas.

Not part of any specification.

• -moz-element