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Math.random() Method in JS – How to Generate Random Numbers

Whenever you invoke Math.random(), the method returns a random number between zero (inclusive) and one (exclusive).

In other words, Math.random() outputs a random number that is equal to or greater than zero (0) but less than one (1).

note

Syntax of the Math.random() Method​

Math.random() accepts no argument. Here is the syntax:

Math.random();

Examples​

Below are examples of the Math.random() method.

How to get a random number between 0 (inclusive) and 1 (exclusive)​

Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).

Math.random();

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How to get a random number between 0 (inclusive) and 1 (inclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Add 1 to the maximum value (1).
  3. Multiply step one's output with step two's result to get a random number between 0 (inclusive) and 1 (inclusive).
Math.random() * (1 + 1);

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How to get a random number between 0 (inclusive) and 3 (exclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Multiply Math.random()'s output by 3 to get a random number between 0 (inclusive) and 3 (exclusive).
Math.random() * 3;

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How to get a random number between 0 (inclusive) and 3 (inclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Add 1 to the maximum value (3).
  3. Multiply step one's output with step two's result to get a random number between 0 (inclusive) and 3 (inclusive).
Math.random() * (3 + 1);

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How to get a random integer between 0 (inclusive) and 3 (exclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Multiply Math.random()'s output by 3 to get a random number between 0 (inclusive) and 3 (exclusive).
  3. Use the Math.floor() method to round down step two's result to the nearest integer.
const randomNumberBetweenZeroAndOne = Math.random();
const randomNumberBetweenZeroAndThree = randomNumberBetweenZeroAndOne * 3;
const randomIntegerBetweenZeroAndThree = Math.floor(
  randomNumberBetweenZeroAndThree
);

// Log randomIntegerBetweenZeroAndThree to the console:
console.log(randomIntegerBetweenZeroAndThree);

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How to get a random integer between 0 (inclusive) and 3 (inclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Add 1 to the maximum value (3).
  3. Multiply step one's output with step two's result to get a random number between 0 (inclusive) and 3 (inclusive).
  4. Use the Math.floor() method to round down step three's result to the nearest integer.
const randomNumberBetweenZeroAndOne = Math.random();
const maximumValuePlusOne = 3 + 1;
const randomNumberRangingFromZeroToThree =
  randomNumberBetweenZeroAndOne * maximumValuePlusOne;
const randomIntegerRangingFromZeroToThree = Math.floor(
  randomNumberRangingFromZeroToThree
);

// Log randomIntegerRangingFromZeroToThree to the console:
console.log(randomIntegerRangingFromZeroToThree);

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How to get a random number between 5 (inclusive) and 10 (exclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Multiply Math.random()'s output with the difference between the maximum (10) and the minimum (5) value to get a random number between 0 (inclusive) and 5 (exclusive).
  3. Add the minimum value (5) to step two's result to get a random number between 5 (inclusive) and 10 (exclusive).
Math.random() * (10 - 5) + 5;

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How to get a random number between 5 (inclusive) and 10 (inclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Subtract the minimum value (5) from the maximum (10).
  3. Add 1 to step two's result.
  4. Multiply step one's output with step three's result to get a random number between 0 (inclusive) and 5 (inclusive).
  5. Add the minimum value (5) to step four's result to get a random number between 5 (inclusive) and 10 (inclusive).
Math.random() * (10 - 5 + 1) + 5;

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How to get a random integer between 5 (inclusive) and 10 (inclusive)​

  1. Invoke Math.random() to get a random number between 0 (inclusive) and 1 (exclusive).
  2. Subtract the minimum value (5) from the maximum (10).
  3. Add 1 to step two's result.
  4. Multiply step one's output with step three's result to get a random number between 0 (inclusive) and 5 (inclusive).
  5. Add the minimum value (5) to step four's result to get a random number between 5 (inclusive) and 10 (inclusive).
  6. Use the Math.floor() method to round down step five's result to the nearest integer.
const randomNumberBetweenZeroAndOne = Math.random();
const maximumMinusMinimumValue = 10 - 5;
const maximumMinusMinimumValuePlusOne = maximumMinusMinimumValue + 1;
const randomNumberRangingFromZeroToFive =
  randomNumberBetweenZeroAndOne * maximumMinusMinimumValuePlusOne;
const randomNumberRangingFromFiveToTen = randomNumberRangingFromZeroToFive + 5;
const randomIntegerRangingFromFiveToTen = Math.floor(
  randomNumberRangingFromFiveToTen
);

// Log randomIntegerRangingFromFiveToTen to the console:
console.log(randomIntegerRangingFromFiveToTen);

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Overview​

This article discussed what JavaScript's Math.random() method does. We also used examples to see how it works.