CanvasRenderingContext2D.setLineDash

The setLineDash() method of the Canvas 2D API's CanvasRenderingContext2D interface sets the line dash pattern used when stroking lines, using an array of values which specify alternating lengths of lines and gaps which describe the pattern.

Syntax

ctx.setLineDash(segments);

Parameters

segments

An Array of numbers which 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

undefined.

Examples

This is just a simple code snippet which uses the setLineDash() method to draw a dashed line above a solid line.

HTML

<canvas id="canvas"></canvas>

JavaScript

var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');

ctx.beginPath();
ctx.setLineDash([5, 15]);
ctx.moveTo(0, 50);
ctx.lineTo(400, 50);
ctx.stroke();

ctx.beginPath();
ctx.setLineDash([]);
ctx.moveTo(0, 150);
ctx.lineTo(400, 150);
ctx.stroke();

Try it

Edit the code below and see your changes update live in the canvas:

Playable code

<canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas>
<div class="playable-buttons">
  <input id="edit" type="button" value="Edit" />
  <input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code" style="height:150px">
ctx.beginPath();
ctx.setLineDash([5, 15]);
ctx.moveTo(0, 50);
ctx.lineTo(400, 50);
ctx.stroke();

ctx.beginPath();
ctx.setLineDash([]);
ctx.moveTo(0, 150);
ctx.lineTo(400, 150);
ctx.stroke();</textarea>

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var textarea = document.getElementById("code");
var reset = document.getElementById("reset");
var edit = document.getElementById("edit");
var code = textarea.value;

function drawCanvas() {
  ctx.clearRect(0, 0, canvas.width, canvas.height);
  eval(textarea.value);
}

reset.addEventListener("click", function() {
  textarea.value = code;
  drawCanvas();
});

edit.addEventListener("click", function() {
  textarea.focus();
})

textarea.addEventListener("input", drawCanvas);
window.addEventListener("load", drawCanvas);

Specifications

Browser compatibility

Gecko-specific notes

• Starting with Gecko 7.0 (Firefox 7.0 / Thunderbird 7.0 / SeaMonkey 2.4), the non-standard and deprecated property mozDash has been implemented to set and get a dash list. This property will be deprecated and removed in the future, see bug 931389. Use setLineDash() instead.

WebKit-specific notes

• In WebKit-based browsers (e.g. Safari), the non-standard and deprecated property webkitLineDash is implemented besides this method. Use setLineDash() instead.

See also

• The interface defining it, CanvasRenderingContext2D
• CanvasRenderingContext2D.getLineDash()
• CanvasRenderingContext2D.lineDashOffset