Array Cardio #1

filter()

Creates a new array with all elements that pass the test implemented by the provided function.

const inventors = [
  { first: 'Marie', last: 'Curie', year: 1867, passed: 1934 },
  { first: 'Albert', last: 'Einstein', year: 1879, passed: 1955 },
  { first: 'Galileo', last: 'Galilei', year: 1564, passed: 1642 },
  { first: 'Isaac', last: 'Newton', year: 1643, passed: 1727 },
  { first: 'Johannes', last: 'Kepler', year: 1571, passed: 1630 }
];

// Filter the list of inventors for those who were born after 1600
let filter = inventors.filter(inventor => inventor.year > 1600);

console.log(filter);
>>
{
  { first: "Albert", last: "Einstein", year: 1879, passed: 1955 },
  { first: "Isaac", last: "Newton", year: 1643, passed: 1727 },
  { first: 'Marie', last: 'Curie', year: 1867, passed: 1934 },
}

map()

Creates a new array with the results of calling a provided function on every element in the calling array.

// Give us an array of the inventors' first and last names
let names = inventors.map(inventor => `${inventor.first} ${inventor.last}`);

console.log(names);
>> ["Albert Einstein", "Isaac Newton", "Galileo Galilei", "Johannes Kepler", "Nicolaus Copernicus"]

sort()

Sorts the elements of an array in place and returns the array. The sort is not necessarily stable. The default sort order is according to string Unicode code points.

// Sort the inventors by birthdate, oldest to youngest
let sortByBirthday = inventors.sort((a, b) => a.year - b.year);

console.table(sortByBirthday);

{ first: "Nicolaus", last: "Copernicus", year: 1473, passed: 1543 },
{ first: "Galileo", last: "Galilei", year: 1564, passed: 1642 },
{ first: "Johannes", last: "Kepler", year: 1571, passed: 1630 },
{ first: "Isaac", last: "Newton", year: 1643, passed: 1727 },
{ first: "Albert", last: "Einstein", year: 1879, passed: 195 5}

reduce()

Applies a function against an accumulator and each element in the array (from left to right) to reduce it to a single value.

// How many years did all the inventors live?
let sumAge = inventors.reduce((acc, currVal) => acc + currVal.passed - currVal.year, 0);

console.log('Sum:', sumAge);
>> Sum: 861

Array.from()

Creates a new Array instance from an array-like or iterable object.

<!-- Create a list of Boulevards in Paris that contain 'of' anywhere in the name -->
<div class="links">
  <a href="/wiki/#1">Boulevards of Paris</a>
  <a href="/wiki/#2">Boulevard Saint-Michel</a>
  <a href="/wiki/#3">City Gates of Paris</a>
  <a href="/wiki/#4">Boulevard des Capucines</a>
</div>

let boulevards = Array.from(document.querySelectorAll('.links a'));
boulevardsWithOf = boulevards.filter(boulevard => boulevard.textContent.includes('of'));

console.log(boulevardsWithOf);
>> [Boulevards of Paris, City Gates of Paris]

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