I am a beginner of javascript learner. Still can't grasp the function concept so far :-(. Now trying to code this game. Since It only return the "else" value (Tie), Is anyone can tell what's the main problem in my code? (I know there's a lot of problem:-()

function getComputerChoice () {
    const myArray=["Rock" , "Paper", "Scissors"]
    
    const random = Math.floor(Math.random() * myArray.length);
    console.log(random, myArray[random]);
}

function playRound(playerSelection, computerSelection) {
    if (playerSelection === "Rock" && computerSelection === "Paper") {
        return("You Lose! Paper beats Rock");
    } else if (playerSelection === 'Paper' && computerSelection === "Scissors") {
        return("You Lose! Scissors beats Paper");
    } else if (playerSelection === "Scissors" && computerSelection === "Rock") {
        return("You Lose! Rock beats Scissors");
    }  else if (playerSelection === "Rock" && computerSelection === "Scissors") {
        return("You Win! Rock beats Scissors");
    }  else if (playerSelection === "Paper" && computerSelection === "Rock") {     
        return("You Win! Paper beats Rock");
    } else if (playerSelection === "Scissors" && computerSelection === "Paper") {
        return("You Win! Scissors beats Paper");
    } else {
        return("It's tie")
    }
}

const playerSelection = "rock";
const computerSelection = getComputerChoice();

function game() {
    for (let i = 0; i < 5; i  ) {
        var result = playRound.call(this, playerSelection, computerSelection)
        console.log(result)
    }
}
game()

enter image description here

CodePudding user response：

You are not returning any data in your getComputerChoice function, computerSelection variable is undefined.

function getComputerChoice () {
    const myArray=["Rock" , "Paper", "Scissors"]
    const random = Math.floor(Math.random() * myArray.length);
    
    return myArray[random]
}

and notice your playerSelection variable, it's lowercase

const playerSelection = "rock"; // should be "Rock"

CodePudding user response：

In the game() section you are passing three parameters in playRound() when the function is defined with only two. Try this:

var result = playRound(playerSelection, computerSelection);

Also, change all your triple quotes to doubles.

I'm sure others will find more suggestions, I'm only learning too so I hope this is actually helpful.

CodePudding user response：

As noted in other answers, your playerSelection value is a lowercase string i.e. not equal to it's capitalized form.

Though that can just be fixed by changing "rock" to "Rock" in the declaration of your constant, this type of issue is the reason why constants exist in programming (among other reasons).

Best Practice with Magic Strings

Notice that you have "Rock", "Paper" and "Scissors" written many times throughout your code. These are called magic strings:

Magic strings are string values that are specified directly within application code that have an impact on the application's behavior.

It's a good practice to store your magic strings inside constants, and then reference those constants throughout your code. This habit will save you the headache of having unnoticed human typos in your magic strings.

Here's what your code would look like having all the magic strings stored in constants (declared once):

const ROCK = "rock";
const PAPER = "paper";
const SCISSORS = "scissors";

// Declare choices array outside a function scope
// so it's only declared once
const CHOICES = [ROCK, PAPER, SCISSORS]

function getComputerChoice () {    
    const random = Math.floor(Math.random() * CHOICES.length);
}

function playRound(playerSelection, computerSelection) {
    if (playerSelection === ROCK && computerSelection === PAPER) {
        return("You Lose! Paper beats Rock");
    } else if (playerSelection === PAPER && computerSelection === SCISSORS) {
        return("You Lose! Scissors beats Paper");
    } else if (playerSelection === SCISSORS && computerSelection === ROCK) {
        return("You Lose! Rock beats Scissors");
    }  else if (playerSelection === ROCK && computerSelection === SCISSORS) {
        return("You Win! Rock beats Scissors");
    }  else if (playerSelection === PAPER && computerSelection === ROCK) {     
        return("You Win! Paper beats Rock");
    } else if (playerSelection === SCISSORS && computerSelection === PAPER) {
        return("You Win! Scissors beats Paper");
    } else {
        return("It's tie")
    }
}

// if the player has to write down their choice, transform it with String.toLowerCase()
const playerSelection = ROCK;
const computerSelection = getComputerChoice();

function game() {
    for (let i = 0; i < 5; i  ) {
        var result = playRound.call(this, playerSelection, computerSelection)
        console.log(result)
    }
}
game()

I hope you find this tip helpful in the future! :)