You can use Array.prototype.filter and filter out the items which are numbers using the typeof operator.

const 
  arr = ["a", "b", "1", 4, 6, "John", 9, 91],
  nums = arr.filter((a) => typeof a === "number");

console.log(nums);

Another approach

You can also do it coercing the items to a number. The strings which cannot be coerced to a number result in NaN, a falsy value in JS, and hence are filtered out.

const 
  arr = ["a", "b", 1, 4, 6, "John", 9, 91],
  nums = arr.filter(Number);

console.log(nums);

But note strings that can be coerced to numbers like "1", "123" etc will not get filtered out by the second approach.

And more importantly this approach would filter out all zeroes (0, "0") in the array as 0 is a falsy value in JS.

const 
  arr = ["1", "4", "6", 0, "0"],
  nums = arr.filter(Number);

console.log(nums);

Filtering Integers

You can also filter only integers using Number.isInteger

const 
  arr = ["1", 2, -3, 4.5],
  ints = arr.filter(Number.isInteger);

console.log(ints);

But note, this approach would not filter out numbers where the integral part of the number is equal to the number itself. In other words simply appending zeroes after the decimal point (like 1.00000) would not yield false when passed to isInteger.

const 
  arr = [1.0, 2.01],
  ints = arr.filter(Number.isInteger);

console.log(ints);

try this:

arr.filter((elem) => Number.isInteger(elem));

output = [1,4,6,9,91]

   const arr = ['a', 'b', 1, 4, 6, 'John', 9, 91];

const number = arr.filter(item => typeof item === 'number')
console.log(number )

here the correct way