To add image to canvas with JavaScript, we call the drawImage method.
For instance, we write
const canvas = document.getElementById("viewport");
const context = canvas.getContext("2d");
const baseImage = new Image();
baseImage.src = "img/base.png";
baseImage.onload = () => {
context.drawImage(baseImage, 0, 0);
};
to select the canvas with getElementById.
And we get its context with getContext.
Next we create an img element with the Image constructor.
And then we call drawImage with baseImage when the image is loaded.
We load the image by setting the src property to the image URL string.