Mutator Methods.

push() - 0(1)

Add a new element to the end of the array.

const names = ['Luis','John','Jose'];
names.push("Aaron");
console.log(names); // (4) ["Luis", "John", "Jose", "Aaron"]

pop() - 0(1)

Delete the last element of the array

const names = ['Luis','John','Jose','Aaron'];
console.log(names.pop()); //Aaron
console.log(names); // (3) ["Luis", "John", "Jose"]

shift() - 0(n)

Delete the first element of the array

const names = ['Luis','John','Jose','Aaron'];
console.log(names.shift()); // Luis
console.log(names); // (3) ["John", "Jose", "Aaron"]

unshift() - 0(n)

Add one or more elements in the beginning of the array

const names = ['Luis','John','Jose'];
console.log(names.unshift("Aaron")); // 4
console.log(names); // (4) ["Aaron", "Luis", "John", "Jose"]

splice() - 0(n)

Remove, add or replace a new element indicate by index.

const names = ['Luis','John','Jose','Aaron'];
console.log(names.splice(0,0,"Fernando")); // Add Michelle
console.log(names.splice(0,1,"Michelle")); // replace Fernando to Michelle
console.log(names.splice(0,1)); // remove Michelle
console.log(names);

sort() - 0(n log(n))

Modify the array, ordered by a compare Function, or if this compare function is not provided the default order is by the position of the Unicode values in the array.

const names = ['Luis','Jose','John','Aaron'];
console.log(names.sort()); // (4) ["Aaron", "John", "Jose", "Luis"]

/*complex sorting*/
const users = [
    {name:'Luis', age:25},
    {name:'Jose', age:20},
    {name:'Aaron', age:40}
];
const compareFuc = (item1,item2) => {
  return item1.age - item2.age;
};
console.log(users.sort(compareFuc));
/**
 [{name: "Jose", age: 20}, {name: "Luis", age: 25}, {name: "Aaron", age:40}]
 */

Accessor methods

concat() - 0(n)

Create a new array with the union of two or more arrays.

const names1 = ["Luis","Jose"];
const names2 = ["John","Aaron"];
const newArray = names1.concat(names2,["Michelle"]);
console.log(newArray); // (5) ["Luis", "Jose", "John", "Aaron", "Michelle"]

slice() - 0(n)

Return a copy of a sub array between two index, start and end. Important Note: if you modify the original array, the value also will be modify in the copy array.

const users = [
  {name:'Luis', age:15},
  {name:'Jose', age:18},
  {name:'Aaron', age:40}
];

const  adults = users.slice(1, users.length);
console.log(adults); // (2) [{name: "Jose", age: 18}, {name: "Aaron", age: 40}]

indexOf() - 0(n)

Return the first index of the element that exists in the array, and if not exists return-1.

const names = ['Luis','Jose','John','Aaron'];
console.log(names.indexOf("John")); // 2
console.log(names.indexOf("Michelle")); // -1

Iteration methods

forEach() - 0(n)

Just execute a function for each element in the array.

const names = ['Luis','Jose','John','Aaron'];

names.forEach(item => {
    console.log(item);
});

map() - 0(n)

Create a new array with the result of the callback function (this function is executed for each item same as forEach)

const users = [
    {name:'Luis', age:15},
    {name:'Jose', age:18},
    {name:'Aaron', age:40}
];
const userDescriptions = users.map(item => {
   return `Hello my name is ${item.name} and I have ${item.age} years old.`
});
console.log(userDescriptions); 
/*["Hello my name is Luis and I have 15 years old.",
 "Hello my name is Jose and I have 18 years old.",
 "Hello my name is Aaron and I have 40 years old."] */

filter() - 0(n)

Create a new array with the elements that apply the given filter condition as true.

const users = [
  {name:'Luis', admin:true},
  {name:'Jose', admin:true},
  {name:'Aaron'}
];
const adminUsers =  users.filter(item => item.admin);
console.log(adminUsers); // [{name: "Luis", admin: true},{name: "Jose", admin: true}]

reduce() - 0(n)

Return a single value after applying the reduction function for each element.

const users = [
  {name:'Luis', age:15},
  {name:'Jose', age:18},
  {name:'Aaron', age:40}
];

const reducer= (accumulator, item)=> accumulator + item.age;
const totalAge =  users.reduce(reducer,0);
const ageAverage = totalAge / users.length;
console.log(`Total ${totalAge}, Average ${ageAverage}`); // Total 73, Average 24.333333333333332

some() - 0(n)

Return a boolean value as true if found one or more item that apply the given condition, and return false if not (also if the array is empty).

const users = [
  {name:'Luis', admin:true},
  {name:'Jose'},
  {name:'Aaron'}
];
const adminExists = users.some(item => item.admin);
console.log(adminExists); // true

every() - 0(n)

This function Return a boolean value as true if all the items apply the given condition, and false if not.

const users = [
  {name:'Luis', active:true},
  {name:'Jose', active:true},
  {name:'Aaron', active:false}
];
const isAllUsersActive = users.every(item => item.active);
console.log(isAllUsersActive); // false