Math.min.apply returns 0 for null

Question

I would like to get minimum value from an array. If the data contains null value, Math.min.apply returns 0 for null value. Please see this JSFiddle example. How can I get true minimum value even if null value exists in array?

Code (same as in JSFiddle example):

var arrayObject= [ {"x": 1, "y": 5}, {"x": 2, "y": 2}, {"x": 3, "y": 9}, {"x": 4, "y": null}, {"x": 5, "y": 12} ];

var max = Math.max.apply(Math, arrayObject.map(function(o){return o.y;}));
var min = Math.min.apply(Math, arrayObject.map(function(o){return o.y;}));

$("#max").text(max);
$("#min").text(min);

Answer 1

These are what I've been using in 2020. Slightly shorter code.

const min = (values) => values.reduce((m, v) => (v != null && v < m ? v : m), Infinity);
const max = (values) => values.reduce((m, v) => (v != null && v > m ? v : m), -Infinity);

const arrayObject = [
  { x: 1, y: 5 },
  { x: 2, y: 2 },
  { x: 3, y: 9 },
  { x: 4, y: undefined },
  { x: 5, y: 12 },
];
const yValues = arrayObject.map((item) => item.y)

console.log(yValues)
console.log('min', min(yValues))
console.log('max', max(yValues))

Answer 2

Well, the numerical value for null is 0. If you don't want null values to be be considered, you have to filter them out:

var values = arrayObject.map(function(o){
    return o.y;
}).filter(function(val) {
    return val !== null
});

Reference: Array#filter

Answer 3

Alternative to Felix's solution: treat null as + or - infinity for min and max calls, respectively.

var max = Math.max.apply(Math, arrayObject.map(function(o) {
    return o.y == null ? -Infinity : o.y;
}));
var min = Math.min.apply(Math, arrayObject.map(function(o) {
    return o.y == null ? Infinity : o.y;
}));