CanvasRenderingContext2D: setLineDash() method
The setLineDash()
method of the Canvas 2D API's
CanvasRenderingContext2D
interface sets the line dash pattern used when
stroking lines. It uses an array of values that specify alternating lengths of lines
and gaps which describe the pattern.
Note: To return to using solid lines, set the line dash list to an empty array.
Syntax
js
setLineDash(segments)
Parameters
segments
-
An
Array
of numbers that specify distances to alternately draw a line and a gap (in coordinate space units). If the number of elements in the array is odd, the elements of the array get copied and concatenated. For example,[5, 15, 25]
will become[5, 15, 25, 5, 15, 25]
. If the array is empty, the line dash list is cleared and line strokes return to being solid.
Return value
None (undefined
).
Examples
Basic example
This example uses the setLineDash()
method to draw a dashed line above a
solid line.
HTML
html
<canvas id="canvas"></canvas>
JavaScript
js
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
// Dashed line
ctx.beginPath();
ctx.setLineDash([5, 15]);
ctx.moveTo(0, 50);
ctx.lineTo(300, 50);
ctx.stroke();
// Solid line
ctx.beginPath();
ctx.setLineDash([]);
ctx.moveTo(0, 100);
ctx.lineTo(300, 100);
ctx.stroke();
Result
Some common patterns
This example illustrates a variety of common line dash patterns.
HTML
html
<canvas id="canvas"></canvas>
JavaScript
The drawDashedLine()
function created below makes the drawing of multiple
dashed lines simple. It receives a pattern array as its only parameter.
js
function drawDashedLine(pattern) {
ctx.beginPath();
ctx.setLineDash(pattern);
ctx.moveTo(0, y);
ctx.lineTo(300, y);
ctx.stroke();
y += 20;
}
const canvas = document.getElementById("canvas");
const ctx = canvas.getContext("2d");
let y = 15;
drawDashedLine([]);
drawDashedLine([1, 1]);
drawDashedLine([10, 10]);
drawDashedLine([20, 5]);
drawDashedLine([15, 3, 3, 3]);
drawDashedLine([20, 3, 3, 3, 3, 3, 3, 3]);
drawDashedLine([12, 3, 3]); // Equals [12, 3, 3, 12, 3, 3]
Result
Specifications
Specification |
---|
HTML Standard # dom-context-2d-setlinedash-dev |
Browser compatibility
BCD tables only load in the browser
See also
- The interface defining this method:
CanvasRenderingContext2D
CanvasRenderingContext2D.getLineDash()
CanvasRenderingContext2D.lineDashOffset