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The JavaScript Map method is a method that maps an object of key-value pairs with a function. This is done by iterating over the object’s keys and invoking the function with the corresponding values in order.

var arr = [1,2,3,4,5,6,7,8,9,10];

var newArr = arr.map(function(item, index, array) {
  return item * 2;
});

console.log(newArr); // [ 2,4,6,8,10,12,14,16,18,20 ]