Sort an array which contains number and strings

The shortest is probably:

 arr.sort((a, b) => ((typeof b === "number") - (typeof a === "number")) || (a > b ? 1 : -1));

You can sort the numbers first and then the non-numbers by using .filter() to separate both data-types.

See working example below (read code comments for explanation):

const arr = [9, 5, '2', 'ab', '3', -1];

const nums = arr.filter(n => typeof n == "number").sort((a, b) => a - b); // If the data type of a given element is a number store it in this array (and then sort numerically)
const non_nums = arr.filter(x => typeof x != "number").sort(); // Store everything that is not a number in an array (and then sort lexicographically)

const res = [...nums, ...non_nums]; // combine the two arrays
console.log(res); // [-1, 5, 9, "2", "3", "ab"]

It seems you have done most of the work in your second attempt. All I have done here is used Array.concat to join the sorted results of number and char together.

var arr = [9, 5, '2', 'ab', '3', -1] // to be sorted
var number = [];
var char = [];
arr.forEach(a => {
  if (typeof a == 'number') number.push(a);
  else char.push(a);
})


var sorted = number.sort().concat(char.sort());
console.log(sorted)