add questions for-each-map

questions/for-each-map.md

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+### What is the difference between a `.map` loop and a `.forEach` loop
+
+#### Answer
+
+Both loops iterate through the elements in an array. `.map()` maps each element to new element by calling the function on each element and it returns the new array. On the other hand, `.forEach()` executes a callback function for each element but does not return anything.
+
+#### Additional links
+
+* [MDN docs for forEach](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach)
+* [MDN docs for map](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map)
+* [JavaScript — Map vs. ForEach](https://codeburst.io/javascript-map-vs-foreach-f38111822c0f)
+
+#### Good to hear
+
+* If you need to iterate over an array, `.forEach()` is a solid option
+* If you need a result but don't want to mutate original array, `.map()` is the right choice
+
+<!-- tags: (javascript) -->