Closure vs. High Order Functions in JavaScript

index.js

// A closure does not mean that it necessarily is returned by a function.
// A closure generally is a function that has access to the declaration context's scope.

// A closure example without returning a function
var oddNumber = 3;

function isOddNumberIsReallyOdd() {
  return oddNumber % 2 === 1;
}

console.log(isOddNumberIsReallyOdd(oddNumber));
// Output: true

// A closure example with returning a function
function getWordRepeater(n) {
  // return a word that repeated "n" times
  return function(word) {
    let result = "";
    for (let i = 0; i < n; i++) {
      result += word;
    }
    return result;
  };
}

var wordRepeater = getWordRepeater(3);
console.log(wordRepeater("hi"));
// Output: hihihi

// A high order function does mean that it returns a function
function getOddDetector() {
  return n => n % 2 === 1;
}

var oddDetector = getOddDetector();
console.log(oddDetector(4));
// Output: false