Sum without highest and lowest number

Readme.md

Task

Sum all the numbers of a given array ( cq. list ), except the highest and the lowest element ( by value, not by index! ).

The highest or lowest element respectively is a single element at each edge, even if there are more than one with the same value.

Mind the input validation.

Example

{ 6, 2, 1, 8, 10 } => 16
{ 1, 1, 11, 2, 3 } => 6

Input validation

If an empty value ( null, None, Nothing etc. ) is given instead of an array, or the given array is an empty list or a list with only 1 element, return 0.

SumWithoutLowestAndHighestNumber.test.ts

import solution = require('./SumWithoutLowestAndHighestNumber.ts');
import {assert} from "chai";

describe("KataTest", function(){
  it("BasicTests", function(){
    assert.deepEqual(solution.sumArray([ 6, 2, 1, 8, 10 ]), 16);
    assert.deepEqual(solution.sumArray([ 6, 0, 1, 10, 10 ]), 17);
    assert.deepEqual(solution.sumArray([ 1, 1, 11, 2, 3 ]), 6);
    assert.deepEqual(solution.sumArray([ ]), 0);
    assert.deepEqual(solution.sumArray([ 1 ]), 0);
    assert.deepEqual(solution.sumArray(null), 0);
    assert.deepEqual(solution.sumArray(), 0);
  });
});

SumWithoutLowestAndHighestNumber.ts

export function sumArray(array ?: Array<number> | null) : number {
  
  if (array?.length && array.every(a => !isNaN(a + 0))) {
    // sort   
    array.sort((a, b) => a - b);

    // add all numbers except first and last
    let total = 0;
    
    for (let i = 0; i < array.length - 1; i++) {
      if (i === 0 || i === array.length - 1) {
        continue;
      }
    
      total += array[i];
    }
    
    return total;
  }
  
  return 0;
}