javascript into html

I am trying to create a javascript game because it can somehow link to html. So far I tried making the canvas in java script pop up but i only saw a white screen. I just started learning html and atm I want all my code to be in java and just use html to place it on the webpage.
here my html:
`

Space Invaders

`

i'm trying to link this page to my js

here my js
`function setup(){
createCanvas(400,400);
}
function draw(){
background(0);
}`

i'm wanting a 400 by 400 screen to appear on the web page with the background in the square being 0. Can someone tell me why this not working?