The CanvasRenderingContext2D
.lineDashOffset
property of the Canvas 2D API sets the line dash offset, or "phase."
Note: Lines are drawn by calling the stroke()
method.
Syntax
ctx.lineDashOffset = value;
value
- A float specifying the amount of the line dash offset. The default value is
0.0
.
Examples
Offsetting a line dash
This example draws two dashed lines. The first has no dash offset. The second has a dash offset of 4.
HTML
<canvas id="canvas"></canvas>
JavaScript
const canvas = document.getElementById('canvas'); const ctx = canvas.getContext('2d'); ctx.setLineDash([4, 16]); // Dashed line with no offset ctx.beginPath(); ctx.moveTo(0, 50); ctx.lineTo(300, 50); ctx.stroke(); // Dashed line with offset of 4 ctx.beginPath(); ctx.strokeStyle = 'red'; ctx.lineDashOffset = 4; ctx.moveTo(0, 100); ctx.lineTo(300, 100); ctx.stroke();
Result
The line with a dash offset is drawn in red.
Marching ants
The marching ants effect is an animation technique often found in selection tools of computer graphics programs. It helps the user to distinguish the selection border from the image background by animating the border.
HTML
<canvas id="canvas"></canvas>
const canvas = document.getElementById('canvas'); const ctx = canvas.getContext('2d'); let offset = 0; function draw() { ctx.clearRect(0, 0, canvas.width, canvas.height); ctx.setLineDash([4, 2]); ctx.lineDashOffset = -offset; ctx.strokeRect(10, 10, 100, 100); } function march() { offset++; if (offset > 16) { offset = 0; } draw(); setTimeout(march, 20); } march();
Specifications
Specification | Status | Comment |
---|---|---|
HTML Living Standard The definition of 'CanvasRenderingContext2D.lineDashOffset' in that specification. |
Living Standard |
Browser compatibility
The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
Desktop | Mobile | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
lineDashOffset | Chrome Full support Yes | Edge Full support 12 | Firefox
Full support
27
| IE Full support 11 | Opera Full support Yes | Safari Full support Yes | WebView Android Full support Yes | Chrome Android Full support Yes | Firefox Android
Full support
27
| Opera Android Full support Yes | Safari iOS Full support Yes | Samsung Internet Android Full support Yes |
Legend
- Full support
- Full support
- Uses a non-standard name.
- Uses a non-standard name.
See also
- The interface defining this property:
CanvasRenderingContext2D
CanvasRenderingContext2D.getLineDash()
CanvasRenderingContext2D.setLineDash()
- Applying styles and color