javascript-arrays.md

Arrays in Javascript

Arrays are datastructures. Unlike objects, they use indices.

• Declare an array like so: const arrayName = ['array-value', 'array-value2', 'array-value3']

Array Manipulation

Reading content

• arrayName.length How many items are in an array

• arrayName[1] Access content from a known index position

Add to Arrays

• Add element to the end of the array: arrayName.push('content')
• Add element to the beginning of the array arrayName.unshift('content')

Remove items from an array

NOTE: These can be used to assign the value from an array to a variable

• Remove an element from the end of the array. arrayName.pop()
• Remove an item from the start of the array arrayName.shift()

Joining and Splitting Arrays

• const arrayName3 = arrayName1.concat(arrayName2) Merge two or more arrays together
• arrayName.splice(start-number, delete-number, 'content') Remove or replace existing elements or add new elements at the index of the start-number. if the delete number is set to 0, it will just input the new content at whatever index point you specify with the start number

Finding index of something in an array

• arrayName.indexOf('item-name'); This will give you the index position of an array item. works well with splice for when you want to find where something is to replace it.