Generate a negative random number using JavaScript


Ok, so you already know how to generate positive rondom numbers but let’s do it again:

To generate a random number varying from 0 to 9 we will use this code:

This expression on the right of the “=”

  1. produces a random number from 0 to 1 (excluding 1, say 0.917) with Math.random()
  2. multiplies it by 10 (9.71)
  3. removes decimals (9) with Math.floor

For negative values from -9 to 0 we will  simply subtract 9 from the previous result:

Now what if you wanted a rondom integer from -10 to 20… ?
Yes you guessed it right! we will generate a random number from 0 to 30 then substact 10 from it

So the rule is:
To generate a random integer from m to n, here is the code


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