p5.js windowWidth

The windowWidth variable in p5.js is a system variable that is used to store the width of the inner window and it maps to window.innerWidth.
Syntax:

windowWidth

Parameters: This function does not accept any parameter.

Below program illustrates the windowWidth variable in p5.js:
Example-1:

function setup() {

    createCanvas(1000, 400);

    // Set text size to 40px
    textSize(20);
}

function draw() {
    background(200);

    rect(mouseX, mouseY, 30, 30);

    //Use of windowWidth Variable
    text("Window Width is " + windowWidth, 30, 40);
}

Output:

Example-2:

function setup() {

    // set height to window width
    width = windowWidth;

    //create Canvas of size 380*80
    createCanvas(width, 100);
}

function draw() {
    background(220);
    textSize(16);
    textAlign(CENTER);
    fill(color('Green'));

    //use of windowWidth variable
    text("windowWidth of Canvas is : "
         + width, width / 2, height / 2);
}

Output:

Reference: https://p5js.org/reference/#/p5/windowWidth