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1607299168.txt

We will rewrite the JavaScript array map function in a functional manner.
function map(fn) {
  return function(arr) {
    return Array.prototype.map.call(arr, fn)
  }
}
map(function(x) {return x * x}) ([1, 2, 3]) //==>> [ 1, 4, 9 ]
Notice that the arguments are flipped. The function comes first then the array. Also we used Array.prototype.map.call instead of just calling arr.map. This is so that we can use our map function with array like objects, arguments and DOMNodeList.
Say you wanted to get all the emails from a list like this in an array.
var people = [ {name:”John”, email:”john@example.com”},
 {name:”Bill”, email:”bill@example.com”} ]
map(get(‘email’)) (people)
 //===>> [ ‘john@example.com’, ‘bill@example.com’ ]