function preload() {
    a = loadImage('assets/a.png');
}

function setup() {
    createCanvas(windowWidth, windowHeight);
    image(a);
}

function preload() {
    glyphs = [
        loadImage('assets/svg/a.svg'),
        loadImage('assets/svg/b.svg'),
        loadImage('assets/svg/c.svg'),
        loadImage('assets/svg/d.svg'),
        loadImage('assets/svg/e.svg'),
        loadImage('assets/svg/f.svg'),
        loadImage('assets/svg/h.svg'),
        loadImage('assets/svg/i.svg'),
        loadImage('assets/svg/l.svg'),
        loadImage('assets/svg/n.svg'),
        loadImage('assets/svg/o.svg'),
        loadImage('assets/svg/p.svg'),
        loadImage('assets/svg/q.svg'),
        loadImage('assets/svg/r.svg'),
        loadImage('assets/svg/s.svg'),
        loadImage('assets/svg/t.svg'),
        loadImage('assets/svg/u.svg')
    ];
}

function setup() {
    createCanvas(windowWidth, windowHeight);
    frameRate(4);
}

count = 0;
x = 0;
y = 0;

function reset() {
    count = 0;
    x = 0;
    y = 0;
}

function draw() {
    clear();
    if (count < glyphs.length) {
        image(glyphs[count], 0, 0, 1000, 1000, x, y, 180, 180);
        count++;
    } else {
        reset();
    }
}

on = false;

function mouseClicked() {
    on = !on;
    if (on) {
        noLoop();
    } else {
        loop();
    }
}

add looping program prototype