It keeps giving me an error saying that something is wrong, although I followed the challenge's.  Here is my code!

/*************
*OBJECT TYPES
**************/

/******************
*Button Object Type
*******************/

var Button = function(config) {
this.x = config.x || 0;
this.y = config.y || 0;
this.width = config.width || 80;
this.height = config.height || 50;
this.label = config.label || "Click";
this.color = config.color || color(207, 85, 85);
this.onClick = config.onClick || function() {};
};

//draw the button
var btn1 = new Button ({
x:350,
y:350,
width:50,
height:50,
color:color (255,99,25),
label:"Run"
onClick:function () {
rabbits[i].draw ();
}
});
Button.prototype.draw = function() {
if (this.isMouseInside() && mouseIsPressed) {
fill(255, 255, 255);
}
else {
fill(this.color);
}
rectMode(CENTER);
rect(this.x, this.y, this.width, this.height, 5);
fill(0, 0, 0);
textSize(19);
textAlign(CENTER, CENTER);
text(this.label, this.x, this.y);
};

//check if mouse cursor is inside the button
Button.prototype.isMouseInside = function() {
return mouseX > this.x-this.width/2 &&
mouseX < (this.x + this.width/2) &&
mouseY > this.y - this.height/2 &&
mouseY < (this.y + this.height/2);
};

//handle mouse clicks for the button
Button.prototype.handleMouseClick = function() {
if (this.isMouseInside()) {
this.onClick();
}
};

/******************
*Rabbit Object Type
*******************/

var Rabbit = function(x, y){
this.x = x;
this.y = y;
this.speed = 0;
this.angle = 90;
this.steps = 0;
this.FRICTION = 0.2;
this.HOP_SPEED = 3;
};

//make the rabbit hop forward
Rabbit.prototype.hop = function() {
this.speed = this.HOP_SPEED;
};

//update the rabbits position and speed
Rabbit.prototype.update = function() {
this.y -= this.speed;
if(this.speed > 0){
this.speed -= this.FRICTION;
}
else if(this.speed < 0){
this.speed = 0;
}
};

//draw the rabbit
Rabbit.prototype.draw = function() {
ellipseMode(CENTER);
angleMode = "degrees";
translate(this.x, this.y);
rotate(-this.angle-90);
fill(255, 255, 255);
noStroke();
ellipse(0, -7, 2, 5);
fill(0, 0, 0);
ellipse(0, 0, 10, 16);
fill(255, 255, 255);
ellipse(0, 6, 8, 9);
fill(0, 0, 0);
ellipse(0, 9, 6, 8);
triangle(-3, 8, 0, 8, -1, -1);
triangle(3, 8, 0, 8, 2, -1);
fill(255, 255, 255);
stroke(255, 255, 255);
triangle(-1, 12, 1, 12, 0, 13);
resetMatrix();
};

/**************
*MAIN PROGRAM
***************/

/** create object instances **/

//create rabbits
var rabbits = [];
for (var i = 0; i < 4; i++) {
rabbits.push(new Rabbit(50 + 100 * i, 300));
}

//create button
var btn1;

draw = function() {
background(98, 122, 54);

//Draw the finish line
rectMode(CORNER);
stroke(0, 0, 0);
for (var i = 0; i < width - 20; i += 40) {
fill(0, 0, 0);
rect(i, 20, 20, 20);
rect(i + 20, 40, 20, 20);
fill(255, 255, 255);
rect(i+20, 20, 20, 20);
rect(i, 40, 20, 20);
}

//Draw the racers
for (var i = 0; i < rabbits.length; i++) {
rabbits[i].update();
rabbits[i].draw();

if (i < 3 && frameCount % 15 === 0) {
if (random(1) < 0.5) {
rabbits[i].hop();
}
}
}

//Draw the button
btn1.draw();

};

mouseClicked = function() {
btn1.handleMouseClick();
};

And here are the instructions I was given:

var btn1 = new Button({
    x: ,
    y: ,
    width: ,
    height: ,
    color: color(),
    label: ,
    onClick: function() {
        rabbits[].(); 
    }
});