[TIL] 20201130 JavaScript Arrays

Data Structure

A collection of data

 

 

 

Arrays

• Ordered collections of values.
• Examples
  • List of comments on IG post
  • Collection of levels in a game
  • Songs in a playlist
• Ways to Create Arrays

const arr = [];
const strArray = ["orange", "red"];
const numArray = [1, 2, 3];
const mixedArray = [true, "orange", 32];

 

 

 

Array Random Access

• Array Index
  • Each element has a corresponding index, counting starts at 0.
  • Example

const num = [1, 2, 3, 4];
num[2]; //3

 

 

 

Array Methods

• push : add to end
• pop : remove from end
• shift : remove from start
• unshift : add to start
• concat : merge two or more arrays
• indexOf : returns the first index at which a given element can be found in the array, or -1 if not found.
• includes : determines whether an array includes a certain value among its entries, returning boolean value.
• reverse : reverses an array in place. The first element becomes the last, the last the first. Destructive to the original.
• slice : copy a portion of an array
• splice : changes the contents of an array by removing or replacing existing elements and/or adding new elements in place
• sort : sorts the elements of an array in place and returns the sorted array.

 

 

Reference Types & Equality Testing

• Even same-looking arrays are not double nor triple equal, because JavaScript compares references in memory.
• If two array variables have the same reference, one changes together when the other one changes.

 

 

Arrays & Const

• The values of the array can change even when const is used, as long as the reference remains the same.
• Use const with arrays so that random new reference can't be assigned. It's a safety precaution.

 

 

Multi-Dimensional Arrays

• Nested Arrays : Arrays can be stored inside of other arrays.

 

 

 

 

 

 

* This post is a summary of Udemy Course "The Web Developer Bootcamp" by Colt Steele.