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Array '[]'

bladesensei profile image coyla ・2 min read

Array '[]'

All examples are Javascript langage.

One on the must used data structure.

It's used to store one/many data of same nature or different nature, in order to get ALL of this
data in one place (this array).

Examples of arrays

// same nature elements
['apple', 'orange', 'pineapple']

[ {'name': 'Naruto'}, 'Ninja', []]
// -> different nature, the first is an object, second is a string and the third an empty array

Depending on the langage, sometimes we need to use an extra coding instruction or an array variant in order to use 'different nature' arrays.

How to use it

Now we need to see how to create an array, make basics instructions like add elements, delete, get and element. You need to learn how to do it in your langage.

The basics operations:

  • create
//creation 
const fruits = []; 

  • add element(s)
fruits[0] = 'apple' 
fruits[1] = 'orange'
fruits.push('pineapple') // push add an element at the end of the array

//result: ['apple', 'orange', 'pineapple']

  • delete elements(s)
delete fruits[2]
//this is the must primitive way to delete an element but we will see that we don't use it often... most of the time we use 'filters, maps, splice'.

  • find and element(s)
console.log(fruits[1]) //get the second element, 0 is the begining
  • find and specific element(s) with loops and if condition like
fruits.forEach((fruit) => {
  if (fruit === 'orange') console.log(fruit)
})
// we use a forEach iteration to get the orange fruit and print it.

Middle and common operation/function of array

  • add element at the end (push) and begining (shift)
  • delete the last and first element (pop, unshift)
  • concat arrays
  • filter elements
  • map (like convertion)
  • (splice, slice) cut/replace/delete
  • find and replace
  • clone array
  • be confortable with multi dimentional array (array into array)
  • sort an array

Check this to JS array method for all of this operations
https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Array#

Exercises

  • Swap to elements without 3 variables
  • Reverse array
  • Nombre pair le + petit
  • Intersection of array
  • Find Max and Minimum of unsorted array
  • Delete repeated numbers of array
  • Check if contains a number if they Array
  • Not the largest path in path matrix m*m

++ https://www.geeksforgeeks.org/array-data-structure/

Note

Feel free to send to suggest improvement to this post.

Discussion (4)

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kwiat1990 profile image
Mateusz Kwiatkowski • Edited

If you use arrows functions, then I don't see any reason why not to use find instead of forEach. It's simple and more elegant than the forEach loop. Besides, I would rather say this:

fruits[0] = 'apple' 
fruits[1] = 'orange'

is not the ordinary way you add elements to the array.

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bladesensei profile image
coyla Author

Yes you are right for both suggestions,
Usually we use push as basic operation to add element.
I will remain forEach to show that loop is also used to get many elements by condition then i will add find method example too. Thanks

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kwiat1990 profile image
Mateusz Kwiatkowski

I would say that depends on what you need to do, it might be better to use either map or filter, which return a new array. It comes very handy in almost every situation. I used those both methods very often.

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bladesensei profile image
coyla Author

If you are beginner or experimented developer let me know which functions you use the most.. maps ? filters ? push ? [] how you do it in your langage ?