Add loops tips

[Kikobeats]

non-exhaustive list:

• Use the correct loop (while, do, for,...).
• (condition to eval in a for loop.

Related: http://www.w3schools.com/js/js_performance.asp

[Kikobeats]

Strongly related:

• http://jrsinclair.com/articles/2017/javascript-without-loops/
• http://jrsinclair.com/articles/2017/indentation-is-the-enemy-less-complex-javascript/

[tomByrer]

I would not use w3schools for any tips.

variable is used the sum variable is stored on the stack whereas with the array.length-in-a-loop-code it is stored in a register

https://stackoverflow.com/a/17995000/1324588