comparer_function.js

/*

In JS the array.sort() function can take a COMPARE function as an argument argument. The purpose of this function is to define an alternative order.

This is useful in cases where we need to sort an array of JS objects, using a key attribute, such as "ordering".

Example: 

function(a, b) {
  return a - b
}

- If the return is negative, index of a will be smaller than b, i.e a will be sorted before b.
- If the return is positve, index of a will be greater than b, i.e a will be sorted after b.
- If the return i 0, no changes are done to index of a and b.

For example, when we call something like:
[100, 50].sort()
This is what's really happening: [100, 50].sort(function (100 , 50) {return 100 - 50}). Because the result is postive, 100 is sorted after 50.

Use the following compare function to sort an array of JS objects, passing the sorting attribute or key as an argument.
*/

function compare(prop) {
  return function (a, b) {
    if (a[prop] > b[prop]) {
      return 1;
    } else if (a[prop] < b[prop]) {
      return -1;
    }
    return 0;
  };
}

// if sorting attribute is numerical
function compare(sorting_attribute) {
  return function (a, b) {
    return a[sorting_attribute] - b[sorting_attribute];
  };
}