CanvasRenderingContext2D: clearRect() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
The
CanvasRenderingContext2D.clearRect()
method of the Canvas 2D API erases the pixels in a rectangular area by setting them to
transparent black.
Note:
Be aware that clearRect()
may cause unintended
side effects if you're not using paths properly. Make sure to call
beginPath()
before starting to
draw new items after calling clearRect()
.
Syntax
clearRect(x, y, width, height)
The clearRect()
method sets the pixels in a rectangular area to
transparent black (rgb(0 0 0 / 0%)
). The rectangle's top-left corner is at
(x, y)
, and its size is specified by width
and
height
.
Parameters
Return value
None (undefined
).
Examples
Erasing the whole canvas
This code snippet erases the entire canvas. This is commonly required at the start of
each frame in an animation. The dimensions of the cleared area are set to equal the
<canvas>
element's width
and height
attributes.
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
Erasing part of a canvas
This example draws a blue triangle on top of a yellowish background. The
clearRect()
method then erases part of the canvas.
HTML
<canvas id="canvas"></canvas>
JavaScript
The cleared area is rectangular in shape, with its top-left corner at (10, 10). The cleared area has a width of 120 and a height of 100.
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
// Draw yellow background
ctx.beginPath();
ctx.fillStyle = "#ff6";
ctx.fillRect(0, 0, canvas.width, canvas.height);
// Draw blue triangle
ctx.beginPath();
ctx.fillStyle = "blue";
ctx.moveTo(20, 20);
ctx.lineTo(180, 20);
ctx.lineTo(130, 130);
ctx.closePath();
ctx.fill();
// Clear part of the canvas
ctx.clearRect(10, 10, 120, 100);
Result
Specifications
Specification |
---|
HTML Standard # dom-context-2d-clearrect-dev |
Browser compatibility
BCD tables only load in the browser
See also
- The interface defining this method:
CanvasRenderingContext2D
CanvasRenderingContext2D.fillRect()
CanvasRenderingContext2D.strokeRect()