Program works in Java but not JavaScript. Can't figure out why!

This is just a sample of code from a larger program, but even this will not run in JavaScript! I have compared it to other programs on OpenProcessing.org, but haven't had any luck finding important differences. I would appreciate it if you could take a quick look and suggest something to try.

float[] backdrop = new float[160]; 
int PR = 255; 
int PG = 105; 
int PB = 180; 

void setup () {
  size(800, 600);
  backdropgenerate();
  backdroprender();
}

void draw() {
  backdroprender(); 
  drawplayer();
}

void backdropgenerate () {
  for (int i=0;i<160;i=i+2) {
    backdrop[i] = random(0, 800);
    backdrop[i+1] = random(0, 600);
  }
}

void backdroprender () {
  noStroke(); 
  smooth(); 
  fill(225); 
  rect(0, 0, 800, 600);
  int fill = 200; 
  int size = 120; 
  for (int i=0;i<160;i=i+2) {
    if (i>40&&i<80) {
      size = 80;
      fill = 125;
    }
    if (i>80&&i<120) {
      size = 50 ;
      fill = 75 ;
    }
    if (i>120) {
      size = 10;
      fill = 25 ;
    }
    fill(fill);
    if (level == 7) {
        fill(colors[i*4], colors[i*4+1], colors[i*4+2], colors[i*4+3]);
    } 
    ellipse(backdrop[i], backdrop[i+1], size, size);
  }
  fill(0);
  rect(0, 500, 800, 600);
}

void drawplayer() {
  fill(PR, PG, PB);
  ellipse(xpos, ypos-20, 40, 40);
  ellipse(xpos, ypos+20, 45, 45);
  rect(xpos-22, ypos+20, 45, 30);
}