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How to create a Triangle with dash pattern border using FabricJS?
In this tutorial, we are going to create a triangle with a dash pattern border using FabricJS. Triangle is one of the various shapes provided by FabricJS. In order to create a triangle, we will have to create an instance of fabric.Triangle class and add it to the canvas.
We can change the appearance of the dashes of border by using the borderDashArray property. However, our triangle object must have borders enabled in order for this property to work. If the hasBorders property is assigned a false value, this property will not work.
Syntax
new fabric.Triangle({ borderDashArray: Array }: Object)
Parameters
-
Options (optional) ? This parameter is an Object which provides additional customizations to our triangle. Using this parameter, properties such as colour, cursor, stroke width, and a lot of other properties can be changed related to the object of which borderDashArray is a property.
Options Keys
-
borderDashArray ? This property accepts an Array which specifies the dash pattern by stating intervals via an array. For example, [5, 3] creates a pattern with 5px dashes followed by 3px gaps.
Example 1: Creating Dash Pattern Border
Passing borderDashArray as key with a custom value
Let's see a code example to create a dash pattern border using borderDashArray property in FabricJS. In this example, we have used a [7,10] array which tells us that the pattern will be created by drawing a 7px long line followed by a 10px gap and repeating this same pattern over and over.
<!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Passing borderDashArray as key with a custom value</h2>
<p>Select the triangle to see the dash pattern</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiate a triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 60,
width: 100,
height: 70,
fill: "#deb887",
borderColor: "red",
borderDashArray: [7, 10],
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Example 2: Effect of hasBorders Property
Passing hasBorders key with the value "false"
As we can see in this example, even though we have assigned the properties borderColor and borderDashArray proper values, they don't work since the hasBorders property has been set to false. When set to False, the borders of an object are not rendered, making the dash pattern invisible.
<!DOCTYPE html>
<html>
<head>
<!-- Adding the Fabric JS Library-->
<script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/510/fabric.min.js"></script>
</head>
<body>
<h2>Passing hasBorders key with the value "false"</h2>
<p>Select the triangle and observe that its borders have not been rendered.</p>
<canvas id="canvas"></canvas>
<script>
// Initiate a canvas instance
var canvas = new fabric.Canvas("canvas");
canvas.setWidth(document.body.scrollWidth);
canvas.setHeight(250);
// Initiate a triangle object
var triangle = new fabric.Triangle({
left: 105,
top: 60,
width: 100,
height: 70,
fill: "#deb887",
borderColor: "red",
borderDashArray: [7, 10],
hasBorders: false,
});
// Add it to the canvas
canvas.add(triangle);
</script>
</body>
</html>
Key Points
The borderDashArray property only works when borders are enabled (hasBorders: true)
The array values represent alternating dash lengths and gap lengths in pixels
You must select the triangle object to see the dash pattern border
The borderColor property controls the color of the dashed border
Conclusion
The borderDashArray property in FabricJS allows you to create custom dash patterns for triangle borders. Remember that borders must be enabled for this property to take effect, and the triangle must be selected to view the dashed border pattern.
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