05-ArrayMethods.js

// @ts-check

//* ** contact
var zero = 0;
var positiveNumbers = [1, 2, 3];
var negativeNumbers = [-3, -2, -1];
var numbers = negativeNumbers.concat(zero, positiveNumbers);

console.log(numbers);

// console.log(numbers);

//* ** every and some
var isEven = function(x) {
  // returns true if x is a multiple of 2.
  console.log(x);
  return x % 2 === 0;
};
var numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15];

numbers.every(isEven); // is going to execute the function only once

console.log('---');

numbers.some(isEven); // is going to execute the function twice

numbers.forEach(function(x) {
  console.log(x % 2 == 0);
});

console.log(numbers.reverse());

// console.log('*** filter ***');

var evenNumbers = numbers.filter(isEven);

// console.log(evenNumbers);

console.log('*** map ***');

// console.log(numbers.map(isEven));

console.log(
  numbers.reduce(function(previous, current, index) {
    return previous + current;
  })
);

console.log(numbers.sort());

console.log(
  numbers.sort(function(a, b) {
    return a - b;
  })
);

function compare(a, b) {
  if (a < b) {
    return -1;
  }
  if (a > b) {
    return 1;
  }
  // a must be equal to b
  return 0;
}

console.log(numbers.sort(compare));

// Sorting objects

var friends = [
  { name: 'John', age: 30 },
  { name: 'Ana', age: 20 },
  { name: 'Chris', age: 25 }
];

function comparePerson(a, b) {
  if (a.age < b.age) {
    return -1;
  }
  if (a.age > b.age) {
    return 1;
  }
  return 0;
}

console.log(friends.sort(comparePerson));

var names = ['Ana', 'ana', 'john', 'John'];
console.log(names.sort());

console.log(
  names.sort(function(a, b) {
    if (a.toLowerCase() < b.toLowerCase()) {
      return -1;
    }
    if (a.toLowerCase() > b.toLowerCase()) {
      return 1;
    }
    return 0;
  })
);

var names2 = ['Maève', 'Maeve'];
console.log(
  names2.sort(function(a, b) {
    return a.localeCompare(b);
  })
);

//* ** toString
console.log(numbers.toString());

console.log(numbers.indexOf(10));
console.log(numbers.indexOf(100));

numbers.push(10);
console.log(numbers.lastIndexOf(10));
console.log(numbers.lastIndexOf(100));

var numbersString = numbers.join('-');
console.log(numbersString);