Here's a simple JavaScript function that outputs (returns) a random number between 0 (inclusive) and 1 (exclusive):

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function getRandomNumber() {
  return Math.random();
}

console.log(getRandomNumber());
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Explanation:
• Math.random() is a built-in JavaScript function that returns a random floating-point number in the range 0 (inclusive) to 1 (exclusive).
• getRandomNumber() simply wraps Math.random() and returns its value.
• The console.log call prints the random number to the console.

If you need a random number within a specific range, say between a minimum value (min) and a maximum value (max), you can modify the function like this:

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function getRandomInRange(min, max) {
  return Math.random() * (max - min) + min;
}

console.log(getRandomInRange(1, 10));  // Outputs a random number between 1 and 10
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Feel free to adjust the code according to your needs!