# Elegantly calculate the minimum and maximum of a number array simultaneously

In Javascript, given a simple `number[]` array, is there an elegant way to calculate the minimum and maximum values simultaneously, or return `undefined` if the array is empty?

Something like this:

``````const a = [1, 2, 3];
const (min, max) = minMax(a);
``````

Pre-emptive response notes:

1. This is not a duplicate of this question because he is not actually calculating the min and max of the same array, but the min or max of 4 different arrays.

2. I want to calculate these in one pass. Not `[Math.min(a), Math.max(a)]`.

3. I know how to do the obvious way:

``````let min = undefined;
let max = undefined;
for (const x of array) {
min = min === undefined ? x : Math.min(min, x);
max = max === undefined ? x : Math.max(max, x);
}
``````

I am wondering if there is something a bit more elegant, e.g. using `Array.reduce()`.

### 16 thoughts on “Elegantly calculate the minimum and maximum of a number array simultaneously”

1. Using `Array.reduce` and only iterating over the array once. I’m using array destructing assignment to pass back both `min` and `max` values from the function (since JS doesn’t have tuple types). I’m also checking for the edge cases of the array being empty:

``````function minMax(array) {
if (array.length == 0) {
return [undefined, undefined];
}
return array.reduce(([min, max], val) => {
return [Math.min(min, val), Math.max(max, val)];
}, [Number.MAX_VALUE, Number.MIN_VALUE]);
}

function testMinMax(array) {
let [min, max] = minMax(array);
console.log(min, max);
}

testMinMax([]); // logs "undefined undefined"
testMinMax(); // logs "1 1"
testMinMax([1, 2, 3, 4, 5]); // logs "1 5"``````
2. You can use `Array.reduce()` to reduce into any kind of result, it doesn’t have to be the same type. For example, reducing an array of numbers into an output array of two numbers, min and max:

``````const minMax = arr =>
arr.reduce(([min,max=min],num) => [Math.min(num,min),Math.max(num,max)], arr);

const a = [5,2,6,3,3,1,1];
const [min,max] = minMax(a);

console.log("min",min,"max",max);``````

The `reduce` is seeded with the array itself, for brevity and because anything else is somewhat unnecessary. This would mess up arrays of length 1 due to the destructuring, so `max=min` is used to set `max` equal to the first element as a fallback. So cases of array length 1 or 0 are handled.

3. With spread operator combining with Math.min and Math.max

``````const a = [1, 2, 3];

const [min, max] = [Math.min(...a), Math.max(...a)];

console.log({min, max});``````
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