Notes on Day 12 of 30 Days of JavaScript

• notes • series • javascript • javascript30

As a millenial this is my firt time to learn about the “KONAMI Code” from 1980s vide0 game culture.

According to Edwards oh howtogeek.com:

Up, Up, Down, Down, Left, Right, Left, Right, B, A. It’s called the Konami Code, and it often meant the difference between life and death in a video game back in the 1980s.

Table of Contents

Lessons Learned

Array.prototype.push()

push adds one or more elements to the end of an array and returns the length of the array.

const arr = ['a', 'b', 'c', 'd', 'e']
arr.push('f')
> 6

arr.push('g', 'h', 'i', 'j')
> 10

arr.push([1, 2, 3])
> 11

console.log(arr)
> ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', [1, 2, 3]]

Array.prototype.splice()

The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place

const arr = ['a', 'b', 'c', 'd', 'e']
arr.splice(0, arr.length-1)
> ['a', 'b', 'c', 'd']

arr.splice(0, 1)
> ['a']

arr.splice(0, 1, 'A')
console.log(arr)
> ['A', 'b', 'c', 'd', 'e']

arr.splice(0, arr.length, 'f')
console.log(arr)
> ['f']

Array.prototype.join()

The join() method creates and returns a new string by concatenating all of the elements in an array (or an array-like object), separated by commas or a specified separator string. If the array has only one item, then that item will be returned without using the separator.

const months = ['Jan', 'Feb', 'Mar']

elements.join();
> 'Jan,Feb,Mar'

elements.join('');
> 'JanFebMar'

elements.join(' ');
> 'Jan Feb Mar'

elements.join('-');
> 'Jan-Feb-Mar'

const days = ['Sun']
days.join('-')
> 'Sun'

Array.prototype.includes()

The includes() method determines whether an array includes a certain value among its entries, returning true or false as appropriate.

const months = ['Jan', 'Feb', 'Mar', ['Jan']]

months.includes('Jan')
> true

months.includes(['Jan'])
> false

References

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