JavaScript Random

Math.random()

`Math.random()` returns a random number between 0 (inclusive),  and 1 (exclusive):

Example

// Returns a random number:
Math.random();
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`Math.random()` always returns a number lower than 1.

JavaScript Random Integers

`Math.random()` used with `Math.floor()` can be used to return random integers.

There is no such thing as JavaScript integers.

We are talking about numbers with no decimals here.

Example

// Returns a random integer from 0 to 9:
Math.floor(Math.random() * 10);
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Example

// Returns a random integer from 0 to 10:
Math.floor(Math.random() * 11);
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Example

// Returns a random integer from 0 to 99:
Math.floor(Math.random() * 100);
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Example

// Returns a random integer from 0 to 100:
Math.floor(Math.random() * 101);
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Example

// Returns a random integer from 1 to 10:
Math.floor(Math.random() * 10) + 1;
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Example

// Returns a random integer from 1 to 100:
Math.floor(Math.random() * 100) + 1;
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A Proper Random Function

As you can see from the examples above, it might be a good idea to create a proper random function to use for all random integer purposes.

This JavaScript function always returns a random number between min (included) and max (excluded):

Example

function getRndInteger(min, max) {
return Math.floor(Math.random() * (max - min) ) + min;
}
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This JavaScript function always returns a random number between min and max (both included):

Example

function getRndInteger(min, max) {
return Math.floor(Math.random() * (max - min + 1) ) + min;
}
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