How to Draw Graphs with JavaScript on the HTML Canvas | Step-by-Step Tutorial
Understanding the Cartesian Plane in HTML Canvas
Learning how to draw a graph using JavaScript canvas is a great way to connect programming with mathematics.
In this tutorial, we'll show you how to draw a graph using JavaScript canvas.
By setting up the Cartesian coordinate system in JavaScript, you can easily plot points, draw lines, and create interactive graphs.
Unlike graph libraries, this example uses pure JavaScript and the HTML5 canvas element so students can understand the underlying maths.
The Cartesian Plane is the usual graph surface we are taught in school.
It consists of the x and y axes.
However, there is a subtle difference between the way we use graphs and the HTML Canvas:
The y-axis of the HTML Canvas is measured from
the top and increases as you move downwards.
Figure: Cartesian graph compared to HTMLS canvas
Setting Up the Canvas in JavaScript
To begin, we'll use the '<canvas>' element in HTML5. The canvas provides a space where JavaScript can draw shapes, lines, and graphs.
In HTML, the canvas tags would represent something like a graph book; and this graph book is plotted
or drawn on using JavaScript.
Everything in between these tags are processed as code before the browser adds the result to the static HTML mark-up.
Drawing X and Y Axes on HTML5 Canvas
To draw a Cartesian graph in HTML Canvas, we use JavaScript to plot the x and y axes.
Remember the key difference between math graphs and HTML canvas graphs is that the canvas has the y-axis inverted,
so we need to adjust the code accordingly.
Important: If you don't see anything when you try out the canvas tag, it may be that your browser does not
support the canvas tag.
Update the browser to a recent version; or get a different browser.
What You've Learnt on Graphs, HTML5 Canvas and JavaScript
This tutorial showed how to draw graphs in JavaScript using HTML Canvas,
including plotting axes, flipping the y-axis, and graphing equations.
These methods help senior secondary students understand both maths and JavaScript graphics more effectively.
Key Takeaways on HTML5 Canvas and JavaScript
The HTML5 canvas lets you draw shapes and graphs using JavaScript.
The coordinate system in canvas starts at the top-left, so you may need to shift axes for a traditional maths graph look.
You can plot any equation by looping through x-values and computing y-values.
