A gist of my most challenging code from BlairSnake

blair-snake.js

//runs when snake hits food to add length
function eatFood() {
    //if food coordinates equal snake head coordinates, eat food and add length
    if(foodX === snakeHeadX && foodY === snakeHeadY) {
        score++
        foodSound()
        //increases speed every 5 points
        speedIncrease()
        
        var length = snake.length
        //if moving horizontally add length to x-axis
        if(leftPressed || rightPressed) {
            //add food space to snake
            snake.unshift([foodX, foodY])
            //add two units to end of snake
            snake.push([snake[length-1][0], snake[length-1][1]], [snake[length-1][0]+5, snake[length-1][1]])
        }              
        //if moving vertically add length to y-axis
        if(upPressed || downPressed)        
            {
            //add food space to snake
            snake.unshift([foodX, foodY])
            //add two units to end of snake
            snake.push([snake[length-1][0], snake[length-1][1]], [snake[length-1][0], snake[length-1][1]+5])}        
        //reset food location
        randomizeFood()
        //reset food type (burger, pizza, or cherries)
        pickFood()
    } 
}