difference between fetch and pull in github code example

Example 1: difference between foreach and map in js

forEach() just loop through the elements. It's throws away return values and always returns undefined.The result of this method does not give us an output .

map() loop through the elements allocates memory and stores return values by iterating main array

Example:

   var numbers = [2,3,5,7];

   var forEachNum = numbers.forEach(function(number){
      return number
   })
   console.log(forEachNum)
   //output undefined

   var mapNum = numbers.map(function(number){
      return number
   })
   console.log(mapNum)
   //output [2,3,5,7]
map() is faster than forEach()

Example 2: difference between pull and pull request

If you use git pull, you pull the changes from the remote repository
into yours.

If you send a pull request to another repository, you ask their 
maintainers to pull your changes into theirs (you more or less ask
them to use a git pull from your repository).