An array is a common data structure that holds items of the same type, in TypeScript, unlike other languages, an array doesn't have a fixed length. Also, in TypeScript, you don't have to re-organize all elements of an array when makings operations like insert or delete.
Representation
- Elements are the items stored in an array
- Index is the location of an element in an array, it goes from 0 to (array length - 1)
/** An array can be written like this **/
const numbers: number[] = [1, 2, 3, 4]
const names = string[] = ['Snake', 'Ocelot', 'Otacon', 'Naomi']
/** Also can be written using a generic array type, Array<elemType> **/
let list: Array<number> = [1, 2, 3, 4]
let list: Array<string> = ['Snake', 'Ocelot', 'Otacon', 'Naomi']
Basics operations
Traverse - Print all array items one by one
/** 3 ways to iterate an array **/
for(let i=0; i<array.length; i++) {
console.log(array[i])
}
for(const item of array) {
console.log(item)
}
array.forEach(item => {
console.log(item)
})
Insertion - Add an item
/** add to the end **/
array.push(5)
/** add to the beginning **/
array.unshift(0)
/** add in a specific index position **/
array.splice(3, 0, 8) // add 8 in the index 3
Deletion - Remove an item
/** remove from the end **/
array.pop()
/** remove from the beginning **/
array.shift()
/** remove from a specific index position **/
array.splice(2, 1) // remove from index 2
Update - Update an item
/** update element in position 1 **/
array[1] = 7
Search - Search by an item
/** you can traverse an array to find an element by its value, or simply use the .find() function **/
const item = array.find(item => item === 3) // search by an item with value 3
Strings are arrays of characters
All above operations can be performed on strings to solve problems like count the occurrences of a character in a string:
let str = "aabbccdd"
let occurrences = 0
for(let i=0; i < str.length; i++) {
if(str[i] === "c") {
occurrences++
}
}
console.log(occurrences) // prints 2
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