How to create a function that determines value between 2 numbers

Question

I have this range of numbers:

0  -------> 25 ------->  80 ------> 150
    small      medium       large

I want to recieve a number between 0 to 150 and to display whether it is small, medium or big. 30 and 45 are medium because they are between 25 and 80 and 5 is small because it is lower than 25.

I want to create a function that does this matching for this object:

var sizeMap = { small : 25, medium : 80, large : 150 }

(assuming that 0 is the lowest number).

The function should look like:

function returnSize(number) {
    for (item in sizeMap)
       ???????
    return size
}

how do I write this function so it can be flexible for adding new categories (for example: 'extra large' : 250). Should I present the object as an array?

Answer 1

To have a deterministic output, I'd prefer to have an array ordered by the categories in question:

var categories = [ 
  {label: 'small', upTo: 25}, 
  {label: 'medium', upTo: 80}, 
  {label: 'large', upTo: 150} ];

(you can even create this array from your original sizeMap)

And then you can do:

function getSizeCategory(number, categories) {
  for (var i = 0; i < categories.length; ++i) {
    if (number < categories[i].upTo) {
      return categories[i].label;
    }
  }
  throw new Error("not in range!");
}

Answer 2

function returnSize(number, sizeMap) {
    for (var key in sizeMap) {
       if (number < sizeMap[key]) return key;
    }
    return key;
}