Essential Books

Using map to reformat objects in an array

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Array.prototype.map(): Returns a new array with the results of calling a provided function on every element in the original array.

The following code example takes an array of persons and creates a new array containing persons with a ‘fullName’ property 

var personsArray = [
  {
    id: 1,
    firstName: "Malcom",
    lastName: "Reynolds"
  }, {
    id: 2,
    firstName: "Kaylee",
    lastName: "Frye"
  }, {
    id: 3,
    firstName: "Jayne",
    lastName: "Cobb"
  }
];

// Returns a new array of objects made up of full names.
var reformatPersons = function(persons) {
  return persons.map(function(person) {
    // create a new object to store full name.
    var newObj = {};
    newObj["fullName"] = person.firstName + " " + person.lastName;

    // return our new object.
    return newObj;
  });
};

We can now call reformatPersons(personsArray) and received a new array of just the full names of each person. 

var fullNameArray = reformatPersons(personsArray);
console.log(fullNameArray);
/// Output
[
  { fullName: "Malcom Reynolds" }, 
  { fullName: "Kaylee Frye" },
  { fullName: "Jayne Cobb" }
]

personsArray and its contents remains unchanged. 

console.log(personsArray);
/// Output
[
  {
    firstName: "Malcom",
    id: 1,
    lastName: "Reynolds"
  }, {
    firstName: "Kaylee",
    id: 2,
    lastName: "Frye"
  }, {
    firstName: "Jayne",
    id: 3,
    lastName: "Cobb"
  }
]
```
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Arrays:
* Syntax
* Remarks
* Converting Array-like Objects to Arrays
* Reducing values
* Mapping values
* Filtering Object Arrays
* Sorting Arrays
* Iteration
* Removing duplicate elements
* Destructuring an array
* Array comparison
* Reversing arrays
* Concatenating Arrays
* Shallow cloning an array
* Merge two array as key value pair
* Array spread rest
* Finding the minimum or maximum element
* Removing items from an array
* Filtering values
* Standard array initialization
* Removing all elements
* Searching an Array
* Convert a String to an Array
* Joining array elements in a string
* Removing / adding elements using splice
* The entries() method
* Remove value from array
* Logical connective of values
* Flattening Arrays
* Object keys and values to array
* Append / prepend items to array
* Checking if an object is an array
* Sorting multidimensional array
* Insert an item into an array at a specific index
* Test all array items for equality
* Copy part of an array with slice()
* Using map to reformat objects in an array
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