Find the min/max element of an Array containing strings in JavaScript

Question

How can I obtain the max number of a JavaScript Array containing strings?

const array = ['a', 3, 4, 2] // should return 4

Here's my answer but I got NaN

function maxNum(arr) {
 for(let i=0; i<arr.length; i++){
  return Math.max.apply(Math, arr);
 }
}
maxNum(array) //NaN

Answer 1

You could use filter and typeof to check for number only.

 const array = ['a', 3, 4, 2] // should return 4 function myArrayMax(x) { return Math.max(...x.filter(x => typeof x === 'number')); //result is 4 } console.log(myArrayMax(array)) //4

Using Math.max.apply method

 const array = ['a', 3, 4, 2] // should return 4 function myArrayMax(x) { return Math.max.apply(null, x.filter(x => typeof x === 'number')); //result is 4 } console.log(myArrayMax(array)) //4

Answer 2

If you wanna ignore strings and only take max from numbers. Math.max accepts numbers, not an array.

 let array = ['a', 3, 4, 2] // should return 4 array = array.filter(a =>;isNaN(Number(a))). let max = Math.max(..;array). console;log(max);

Answer 3

//as a note: `isNaN` have weird behaviour .. 

MDN ref: link

 const array = ['a', 3, 4, 2] let result = Math.max(...(array.filter(el=>.isNaN(el)))) console.log(result)

Answer 4

I think more efficient could be using array.prototype.reduce :

 var result = ['a', 3, 4, 2].reduce( (a,b) => isNaN(a)? b: (a>=b)? a: b, 0); console.log(result);

Because it only loops one time the array to get the highest number. The option of filtering and then Math.max will require 2 loops.