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Fabric.js | Triangle borderOpacityWhenMoving Property

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  • Last Updated : 02 Feb, 2021
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In this article, we are going to see how to draw a canvas Triangle in which border opacity will change when user is moving the triangle using FabricJS. The canvas triangle means the triangle is movable and can be stretched according to requirement. Further, the triangle can be customized when it comes to initial stroke color, height, width, fill, or stroke width.

To make this possible we are going to use a JavaScript library called FabricJS. After importing the library, we will create a canvas block in the body tag which will contain the triangle. After this, we will initialize instances of Canvas and triangle provided by FabricJS and enable the borderOpacityWhenMoving of canvas triangle using borderOpacityWhenMoving property and render the triangle on the Canvas as given below.


    width: number,
    height: number,
    borderOpacityWhenMoving: number

Parameters: This function accepts three parameters as mentioned above and described below: 

  • width: It specifies the width of triangle.
  • height: It specifies the height of triangle.
  • borderOpacityWhenMoving: This parameter defines the border opacity of the triangle.

Example: This example uses FabricJS to enable the borderOpacityWhenMoving of the canvas-like triangle as given below. Try borderOpacityWhenMoving the object after enabling borderOpacityWhenMoving property, it will changed the opacity of the triangle border by defined number.



<!DOCTYPE html>
        Fabric.js | Triangle borderOpacityWhenMoving Property
    <!-- Adding the FabricJS library -->
    <script src=
        <div style="text-align: center;width: 600px;">
        <h1 style="color: green;">
            Fabric.js | Triangle borderOpacityWhenMoving Property
    <canvas id="canvas" width="600" height="200"
        style="border:1px solid #000000">
        // Initiate a Canvas instance
        var canvas = new fabric.Canvas("canvas");
        // Initiate a triangle instance
        var triangle = new fabric.Triangle({
                        width: 150,
                        height: 100,
                        fill: '',
                        stroke: 'green',
                        strokeWidth: 3,
                        cornerColor: 'blue',
                        borderOpacityWhenMoving: 0.2
        // Render the triangle in canvas



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