One of my first programs (2013)

calculator.js

var pr = 365;
var sy = 200;
var sx = 120;
var a1 = 0;
var a = 0;
var ap = a;
var b1 = 0;
var b = 0;
var bp = b;
var c = 0;
var wait = 0;
var wy = 0;
var li = 0;
var zw = 0;
var guzik = function(x,y,n,s){
    fill(255, 0, 0);
    strokeWeight(2);
    rect(x,y,s,s);
    textSize(s);
    fill(0, 0, 255);
    text(n,x+8,y+29);
    if(wait%4===0){
        if(mouseX>x&&mouseY>y&&mouseX<x+s&&mouseY<y+s&&mouseIsPressed){
            if(li===0){
                a = a*10+n;
            }
            else{
                b = b*10+n;
            }
            wy = 0;
        }
    }
};
var reset = function(x,y,r,s){
    fill(255, 0, 0);
    strokeWeight(2);
    rect(x,y,s,s);
    textSize(s);
    fill(0, 0, 255);
    text(r,x+4,y+30);
    if(wait%4===0){
        if(mouseX>x&&mouseY>y&&mouseX<x+s&&mouseY<y+s&&mouseIsPressed){
            a = 0;
            b = 0;
            c = 0;
            pr = 365;
            a1 = a;
            wy = 0;
            li = 0;
            zw=0;
        }
    }
};
var znak = function(x,y,z,s){
    fill(255, 0, 0);
    strokeWeight(2);
    rect(x,y,s,s);
    fill(0, 0, 255);
    text(z,x+9,y+29);
    if(wait%4===0){
        if(mouseX>x&&mouseY>y&&mouseX<x+s&&mouseY<y+s&&mouseIsPressed){
            if(li===1){
                c=a;
                pr=365;
            }
            if(z==="="){
                wy = 1;
                if(zw==="+"){
                    c=a+b;
                }
                if(zw==="-"){
                    c=a-b;
                }
                if(zw==="*"){
                    c=a*b;
                }
                if(zw==="/"){
                    c=a/b;
                }
            }
            else{
                li = 1;
                pr=365;
                zw=z;
            }
        }
    }
};
var draw = function() {
    background(0, 0, 0);
    wait = wait+1;
    fill(255, 0, 0);
    rect(25,20,350,120);
    fill(0, 0, 255);
    textSize(40);
        if(b>1000000000){
        b = bp;
    }
    else{
        bp = b;
    }
    if(b>b1){
        if(b<=1000000000){
            pr = pr-22;
            b1 = b;
        }
    }
    if(a>1000000000){
        a = ap;
    }
    else{
        ap = a;
    }
    if(a>a1){
        if(a<=1000000000){
            pr = pr-22;
            a1 = a;
        }
    }
    if(li===0){
        if(a>0){
            text(a,pr,55);       
        }
    }
    else{
        if(b>0){
            text(b,pr,55);       
        }
    }
    if(wy===1){
        text(c,32,133);
    }
    guzik(sx,sy+80,1,35);
    guzik(sx+40,sy+80,2,35);
    guzik(sx+80,sy+80,3,35);
    guzik(sx,sy+40,4,35);
    guzik(sx+40,sy+40,5,35);
    guzik(sx+80,sy+40,6,35);
    guzik(sx,sy,7,35);
    guzik(sx+40,sy,8,35);
    guzik(sx+80,sy,9,35);
    guzik(sx+40,sy+120,0,35);
    //println(a+"   "+b);
    znak(sx+120,sy,"+",35);
    znak(sx+120,sy+40,"-",35);
    znak(sx+120,sy+80,"=",35);
    znak(sx+160,sy,"*",35);
    znak(sx+160,sy+40,"/",35);
    reset(sx+160,sy+80,"C",35);
};