This is a simple Rock Paper Scissors game written in JavaScript and played against the computer. The player plays a 5 round game that keeps score and reports whether the player wins or loses at the end. The results are shown in the browser console.
It consists of three functions:
computerPlay()playRound()game()
computerPlay() is used to make the computer's play. It randomly returns 'Rock', 'Paper' or 'Scissors'. This is achieved using an array with the options and the Math.random() and Math.floor() methods.
Math.random() returns a floating-point pseudo-random number between 0 and 1 (1 excluded), which we scale by 3, using the result as input for Math.floor(). This will generate 0, 1 or 2, randomly. We assign this value to a variable called random, using it as an index number to access an element of the array with the options, returning the element.
playRound() is used to play a single round. It takes two parameters - playerSelection and computerSelection - and returns a string that declares the winner of the round or throws an error if the player chooses an invalid option.
The toLowerCase() method is used in playerSelection, and its first letter is capitalized. So, no matter what the player enters (rock, Rock, rocK, etc), it will always be with the first letter capitalized so that the comparisons that follow work.
game() is used to play a 5 round game. A for loop is used to play the 5 rounds. In each iteration, the player enters the choice via the prompt() method, and this choice is stored in the variable playerSelection. The computerPlay() function is called, storing the computer choice in the computerSelection variable. The playRound() function is then called with playerSelection and computerSelection as arguments, storing the returned string in the roundResult variable.
Then, conditional statements (if, else if) are used to give the player or the computer a score based on the content of roundResult (using the includes() method). No one scores in case of a draw.
console.log() is used to inform the round number, the computer choice and the round result.
After the loop ends, a string is stored in the variable message. This string depends on the result of the game. If the player score is greater than the computer score, the string is 'You win!'. If the player score is less than the computer score, the string is 'You lose!'. Otherwise, the string is 'Draw!'. This is achieved using the conditional (ternary) operator '?'. We could use if...else statements, but as this is only a variable assignment that depends on some conditions, it's much shorter and simpler to use the ternary operator.
Then, the game() function returns a string with the player score, the computer score, and the value inside message.
From The Odin Project's curriculum.