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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