indexOf.js

var arr = [
	"Apple",
  "Orange",
  "Pineapple",
  "Mango",
  "Mango",
  "Pear"
];

console.log(arr.indexOf("Orange")) // outputs 1
console.log(arr.indexOf("Watermelon")) // outputs -1
console.log(arr.indexOf("Mango")) // outputs 3

Join.js

var arr = [
  "1",
  "2",
  "3",
  "4",
  "5"
];

var str = arr.join(",");

console.log(str); //outputs 1,2,3,4,5

LastIndexOf.js

var arr = [
	"Apple",
  "Orange",
  "Pineapple",
  "Mango",
  "Mango",
  "Pear"
];

console.log(arr.lastIndexOf("Mango")) // outputs 4

MapArguments.js

var arr = [
  "1",
  "2",
  "3",
  "4",
  "5"
];

function strToNum (str, index, arr) {
  console.log(index);
  console.log(arr);
  return parseInt(str);
}

var newArr = arr.map(strToNum);

console.log(newArr); // [1, 2, 3, 4, 5]

MapSum.js

var arr = [
  "1",
  "2",
  "3",
  "4",
  "5"
];

function strToNum (str) {
  return parseInt(str);
}

var newArr = arr.map(strToNum);

console.log(newArr); // [1, 2, 3, 4, 5]

Push.js

var arr = [
  "1",
  "2",
  "3",
  "4",
  "5"
];

arr.push("6");

console.log(arr); // ["1", "2", "3", "4", "5", "6"]

Slice.js

var arr = [
	"Apple",
  "Orange",
  "Pineapple",
  "Mango",
  "Pear"
];

var begin = 1;
var end = 2;

console.log(arr.slice(begin));
console.log(arr.slice(begin, end));

Spliceadd.js

var arr = [
	"Apple",
  "Orange",
  "Pineapple",
  "Mango",
  "Pear"
];

var index = 0;
var elems = 0;
var newElem = 'Banana';

console.log(arr.splice(index, elems, newElem)) // add elements to starting of an array 
// outputs ["Banana", "Apple", "Orange", "Pineapple", "Mango", "Pear"]

Splicerm.js

var index = 1;
var elems = 2;
var newElem = 'Banana';

console.log(arr.splice(index, elems)) // add elements to starting of an array
console.log(arr) // ["Apple", "Mango", "Pear"]
// console.log(arr.splice(index, elems, 'Banana')) you can also add and remove elements from a given index at the same time.