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exercise 8k i checked my code and its the same but still giving error #132

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unevtable opened this issue Jun 26, 2024 · 7 comments
Open

exercise 8k i checked my code and its the same but still giving error #132

unevtable opened this issue Jun 26, 2024 · 7 comments

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@unevtable
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<!DOCTYPE html>
<html>

<head>
  <title>Coin Flip</title>
</head>

<body>
  <button onclick="
    playGame('HEADS');
  ">Heads</button>
  <button onclick="
    playGame('TAILS');
  ">Tails</button>

  <script>
    const score = JSON.parse(localStorage.getItem('score')) || { wins: 0, losses: 0 };

    function playGame(guess) {
      const randomNumber = Math.random();
      const result = randomNumber < 0.5 ? 'HEADS' : 'TAILS';

      console.log(`ITS ${result}!`);

      console.log(guess === result ? 'You Win!' : 'You Lose!');

      guess === result ? score.wins++ : score.losses++;
      console.log(score);

      localStorage.setItem('score', JSON.stringify(score));
    }
  </script>
</body>

</html>
@unevtable
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image

@kavin00111
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Its working correctly I don't think there is any error

@MoudiZd
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MoudiZd commented Jun 30, 2024

I think its about javascript version inside browser

What is the browser you are using and which version, btw try to update your browser than run your code i think it must works ...

@unevtable
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i am using edge and it is the latest version

@MoudiZd
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MoudiZd commented Jul 1, 2024 •
edited
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Try to change this line :
const score = JSON.parse(localStorage.getItem('score')) || { wins: 0, losses: 0 };

into

const score = JSON.parse(localStorage.getItem('score')||null) || { wins: 0, losses: 0 };

@unevtable
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can you please explain this

@MoudiZd
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MoudiZd commented Jul 2, 2024 •
edited
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can you please explain this

First let tell what is the problem:

Using JSON.parse(null); will result null, while using JSON.parse(undefined); throws an exception and stop the script

For some reason using localStorage.getItem('score'); on microsoft edge returns undefined (browser specific behavior...)

So using :
JSON.parse(localStorage.getItem('score')) || {wins: 0,losses: 0};

Will be equal to:
JSON.parse(undefined) || {wins: 0,losses: 0}

And because:
JSON.parse(undefined) throws an error this leads to not be fallen back to the passed default object, but instead stop the script

For that we will try to find a way that letJSON.parse not stop the script but results null instead when the passed argument is undefined, and this can be done by adding || null to the argument passed to JSON.parse call

To become:
JSON.parse(localStorage.getItem('score')||null) || { wins: 0, losses: 0 };

In this way the script will not be stopped due passing undefined to JSON.parse call, because it will see that we are passing null instead of undefined (because undefined || null = null) which is acceptable by parsemethod therefore will result overall to return the default object passed after theJSON.parse` call due that the first part of statement is null

Hope that this was clear enough to address the issue

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3 participants
@MoudiZd @unevtable @kavin00111