How to generate a random number between range -100 to 0 and 800 to 900 [duplicate]

How can I generate a number between -100 to 0 and 800 - 900 range.

I want a function that takes 4 arguments 2 min ranges and 2 max ranges and generate a number between those two ranges. and nothing except them.

function numberInRange(min1, min2, max1, max2){
// what to put here
}