无法让我的函数多次运行并破坏我的代码

Question

I'm trying to run this function until the player or the computer wins 5 times. Without the while loop, it runs one time and everything works fine. As soon as I add a while loop, the function still runs only once and it gives me an undefined return.

 function playToFive() { console.log('Let\\'s play Rock Paper Scissors'); var playerWins = 0; var computerWins = 0; while (playerWins === 5 || computerWins === 5) { if (humanVsMachine === 'player') { playerWins += 1; } else if (humanVsMachine === 'computer') { computerWins += 1; } return [playerWins, computerWins]; } } console.log(playToFive()); 

Answer 1

while(playerWins === 5 || computerWins === 5)

Your while loop will actually never execute, since you're checking for equality and both playerWins and computerWins are 0 initially.

You may be looking for a condition more like this:

while(playerWins < 5 && computerWins < 5)

Note that we're using the logical AND && instead of the logical OR || . This is because you don't want to keep looping until both of them win. The logical OR means that even if the computer has won but the player hasn't, we'll continue looping. Only one of the conditions needs to be true for the whole statement to be true.

When we use the logical AND, if one of them is false (meaning, if only one player has reached 5 wins already), then we will break out of the loop as we should.

The next problem is that you have a return statement in your while loop, so after the first execution, even if 5 wins haven't been reached yet, it will return the array of the player's wins and the computer's wins.

You should put the return statement after the loop so that you run the loop 5 times and then return after somebody has won.

And finally, since you haven't provided the rest of the code, I'm not sure if humanVsMachine is actually defined; if you defined that outside of the function then you're good to go.

Answer 2

After the if-else structure is evaluated and executed, a return statement is called unconditionally, thus terminating the loop prematurely. You should place the return after the loop instead. Additionally, the loop condition should be as long as neither player reaches 5 wines (evaluated with the < operator):

while (playerWins < 5 && computerWins < 5 ) {
    if (humanVsMachine === 'player') {
        playerWins +=1;
    } else if (humanVsMachine === 'computer') {
        computerWins += 1;
    }
}
return [playerWins, computerWins];

Answer 3

你需要在while循环之外移动return语句，但是你还需要在while循环中改变你的条件 - 现在只有当playerWins或computerWins正好是5时它才会运行，而实际上它需要停止在那一点上运行（所以while(playerWins < 5 && computerWins < 5) ）

Answer 4

Return will terminate your loop

function returnMe() {
  for (var i=0; i<2; i++) {
    if (i === 1) return i;
  }
}

alert(returnMe()); Try this out 


function playToFive() {
    console.log('Let\'s play Rock Paper Scissors');
    var playerWins = 0;
    var computerWins = 0;
    while (playerWins === 5 || computerWins === 5) {
        if (humanVsMachine === 'player') {
        playerWins += 1;
        } else if (humanVsMachine === 'computer') {
        computerWins += 1;
        }
    // return [playerWins, computerWins]; moving code to below
    }
    return [playerWins, computerWins]; // moved return outside the loop here
}

console.log(playToFive());

Answer 5

You're returning inside the while loop, which will end the looping process. Therefore move your return code outside the loop like below. Also notice that your logical statement is not going to allow the loop to run properly.

function playToFive() {
    console.log('Let\'s play Rock Paper Scissors');
    var playerWins = 0;
    var computerWins = 0;
    while (playerWins < 5 && computerWins < 5 ) {
        if (humanVsMachine === 'player') {
        playerWins += 1;
        } else if (humanVsMachine === 'computer') {
        computerWins += 1;
        }
    // return [playerWins, computerWins]; moving code to below
    }
    return [playerWins, computerWins]; // moved return outside the loop here
}

console.log(playToFive());

Allow me to add that spacing your code helps a lot, it's a little bit 'vertical' looking with the closing brackets. Note how spacing on the above helps to visually identify things like this :)