How to create a canvas with Rectangle using FabricJS?

In this tutorial, we are going to learn how to create a canvas with a Rectangle object using FabricJS. Rectangle is one of the various provided by FabricJS. In order to create a rectangle, we will have to create an instance of fabric.Rect class and add it to the canvas.

Syntax

new fabric.Rect({ width: Number, height: Number }: Object)

Parameters

Options (optional) − This parameter is an Object which provides additional customizations to our rectangle. Using this parameter, properties such as colour, cursor, stroke width, and a lot of other properties can be changed related to the rectangle object of which width and height are properties.

Options Keys

width − This property accepts a Number which specifies the object’s width.
height − This property accepts a Number which specifies the object’s height.

Example 1

Creating an instance of fabric.Rect() and adding it to our canvas

Let’s see a code example of how we can add a rectangle to our canvas. Here we have created an object with a width of 100px and a height of 70px. Also, we have used the colour "green" as a fill colour.

<!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>Creating an instance of fabric.Rect() and adding it to our canvas</h2>
   <p>You can click on the rectangle and interact with it</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 rectangle object
      var rect = new fabric.Rect({
         left: 115,
         top: 50,
         width: 100,
         height: 70,
         fill: "green",
      });

      // Add it to the canvas
      canvas.add(rect);
   </script>
</body>
</html>

Example 2

Manipulating the Rectangle object by using the set method

In this example, we have assigned the properties to the rectangle by using the set method which is a setter for values. Any property related to stroke, strokeWidth, angle, scaling, rotation, etc, can be mutated by using this method.

<!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>Manipulating the Rectangle object by using the set method</h2>
   <p>You can click on the rectangle and interact with it</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 rectangle object
      var rect = new fabric.Rect();
     
      // Using set to set the properties
      rect.set("left", 119);
      rect.set("top", 60);
      rect.set("width", 170);
      rect.set("height", 90);
      rect.set("angle", 45);
      rect.set("fill", "#bdda57");
      rect.set("stroke", "#d9e650");
      rect.set("strokeWidth", 4);

      // Add it to the canvas
      canvas.add(rect);
   </script>
</body>
</html>