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.min and 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 .