We can create a black rectangle on a canvas using fillRect().
As you can see, we provide four arguments to the fillRect() method. These are the values for the x-coordinate, y-coordinate, widthand height` respectively for the rectangle.
So, in the above example, the rectangle's upper-left corner is at 10 on the x-axis, the rectangle's upper-left corner is at 10 on the y-axis, the width of the rectangle is 300px and the length of the rectangle is 50px.