Paul-Browne

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

var total = array.reduceRight(function(accumulator, currentValue, currentIndex, array){
    return accumulator + currentValue;
}, 0)

console.log(total);
// 55 (10 + 9 ... 2 + 1)

Paul-Browne

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

var test = Array.isArray(example);

console.log(test);
// true

Paul-Browne

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

var lastIndexOfOne = array.lastIndexOf(1);
var lastIndexOfFive = array.lastIndexOf(5);
var lastIndexOfTwenty = array.lastIndexOf(20);

console.log(lastIndexOfOne);    // 9
console.log(lastIndexOfFive);   // 5
console.log(lastIndexOfTwenty); // -1 

Paul-Browne

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

var indexOfOne = array.indexOf(1);
var indexOfFive = array.indexOf(5);
var indexOfTwenty = array.indexOf(20);

console.log(indexOfOne);    // 0
console.log(indexOfFive);   // 4
console.log(indexOfTwenty); // -1 

Paul-Browne

var array1 = [1, 2, 3, 4];
var array2 = [5, 6, 7, 8];
var array3 = [9, 10, 11, 12];

var array = array1.concat(array2, array3);

console.log(array);
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

Paul-Browne

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

console.log(array.length);
// 10

Paul-Browne

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

var arrayLength = array.unshift(-2, -1, 0);

console.log(array);
// [-2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

console.log(arrayLength);
// 13

Paul-Browne

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

var removedElement = array.shift();

console.log(array);
// [2, 3, 4, 5, 6, 7, 8, 9, 10]

console.log(removedElement);
// 1

Paul-Browne

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

var removedElement = array.pop();

console.log(array);
// [1, 2, 3, 4, 5, 6, 7, 8, 9]

console.log(removedElement);
// 10

Paul-Browne

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

var arrayLength = array.push(11, 12, 13);

console.log(array);
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]

console.log(arrayLength);
// 13