Author: Chrysto Panayotov

These are two very helpful JavaScript functions if you need to work with ranges and percents.

rangeToPercent

function rangeToPercent(number, min, max){
   return ((number - min) / (max - min));
}

This function returns percentage of a number in a given range. For example rangeToPercent(40,20,60) will return 0.5 (50%). rangeToPercent(34,0,100) will return 0.34 (34%)

percentToRange

function percentToRange(percent, min, max) {
   return((max - min) * percent + min);
}

This function returns number that corresponds to the percentage in a given range. For example percentToRange(0.34,0,100) will return 34.

 

Credits:

Original functions are part of  MathUtils Class by Bruno Imbrizi written in ActionScript3.

This is JS syntax of the AS3 bound() function I use for my flash projects.

function bound(_number, _min, _max){
	return Math.max(Math.min(_number, _max), _min);
}

The function takes 3 parametes:

_number is the number you want to restrict.

_min is the minimal value.

_max is the maximum value.

If the _number is less than _min, the function returns the _min value. If the _number is greater than _max, the function returns _max value. This is a way to ensure you number will be within this minimum and maximum bounds.

Example:

console.log(boundrary(10,5,15));   // returns 10
console.log(boundrary(2,5,15));    // returns 5
console.log(boundrary(100,5,15));  // returns 15

[highlight]Update: 14 aug 2013 [/highlight]

The snippet is can be found at javascriptcookbook website:   http://www.javascriptcookbook.com/article/Restrict-a-number-to-a-range