Find min and max in array of values.

arrayMinMax.js

// Return a tuple of the minimum and maximum values in `arr` array
function arrayMinMax(arr){
  return [...arr].reduce(([min, max], value) => {
    return [
      value < min ? value : min,
      value > max ? value : max
    ];
  }, [Infinity, -Infinity]);
}

// Create a string of `len` copies of string `str`
function stringFill(len, str) {
  return (new Array(len || 1000).fill(str || 'x').join(''));
}

// Modification of above function to find longest string in array of strings
function stringMinMax(strArr) {
  return [...strArr].reduce(([short, long], str) => {
    return [
      str.length < short.length ? str : short,
      str.length > long.length ? str : long
    ];
  }, [stringFill(100), '']);
}