Min/Max across an array of objects

Question

It has been done to death pretty much, here on SO and around the 'Net. However I was wondering if there was a way to leverage the standard min/max functions of:

Array.max = function(array) {
    return Math.max.apply(Math, array);
};

Array.min = function(array) {
    return Math.min.apply(Math, array);
};

So I can search across an array of objects of say:

function Vector(x, y, z) { this.x = x; this.y = y; this.z = z; }
var ArrayVector = [ /* lots of data */ ];
var min_x = ArrayVector.x.min(); // or
var max_y = ArrayVector["y"].max();

Currently I have to loop through the array and compare the object values manually and craft each one to the particular need of the loop. A more general purpose way would be nice (if slightly slower).

Answer 1

You could make some changes to your Array.minand max methods to accept a property name, extract that property of each object in the array, with the help of Array.prototype.map, and the max or min value of those extracted values:

Array.maxProp = function (array, prop) {
  var values = array.map(function (el) {
    return el[prop];
  });
  return Math.max.apply(Math, values);
};

var max_x = Array.maxProp(ArrayVector, 'x');

I just want to mention that the Array.prototype.map method will be available on almost all modern browsers, and it is part of the ECMAScript 5th Edition Specification, but Internet Explorer doesn't have it, however you can easily include an implementation like the found on the Mozilla Developer Center.