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Choose a Random Number Between Two Values

August 15, 2018

4 min read

A simple, but useful utility function to randomly choose a float (whole number with decimal) in a range. The output includes the low number and excludes the high number.

// range: [low, high)
function floatBetween(low, high) {
return Math.random() * (high - low) + low;

From the basic random float in range function, its possible to make a few simple tweaks to guarantee the number is an integer (has no decimal values). Add Math.floor() to round the number down to a whole integer value. This function includes the low number and excludes the high number. By adding 1 to the max value calculation, you can include the high number in your range as well.

// range: [low, high)
function intBetweenExclusive(low, high) {
return Math.floor(Math.random() * (high - low)) + low;
// range: [low, high]
function intBetweenInclusive(low, high) {
return Math.floor(Math.random() * (high - low + 1)) + low;