DEV Community: EmanSaeed331

How can you read a technical book with effective tips from ChatGPT

EmanSaeed331 — Wed, 01 Feb 2023 15:25:38 +0000

Big O

EmanSaeed331 — Tue, 16 Aug 2022 02:04:29 +0000

Big O used to classify algorithms according to how their run time or space.

Big O shorthand

1. Arithmetic operators are constant.
2. Variable assignment is constant.
3. Accessing elements in an array (by index ) or an object (by key ) is constant.
4. in loop the complexity is the length of the loop times the complexity of whatever happens inside this loop.

Space complexity rules

1. Most Primitives (Boolean, numbers , undefined , null ) are constant space .
2. string require O(N) space where n is length of the string.
3. Reference type are generally O(N) space where n is the length (for arrays or the number of keys for objects )

Big O for Objects

1. insertion O(1)
2. Removing O(1)
3. Searching O(N)
4. Accessing O(1)

Big O for Objects Methods

1. Object. Keys O(N)
2. Object. Values O(N)
3. Object. entries O(N)
4. has Own Property O(1)

Big O for arrays

1. insertion O(1) if we insert at the end but at beginning of array O(N)
2. Removing O(1) if we remove at the end but at beginning of array O(N)
3. Searching O(N)
4. Accessing O(1)

Big O for arrays Methods

1. push O(1)
2. pop O(1)
3. shift O(N)
4. unshift O(N)
5. concatenate O(N)
6. slice O(N)
7. splice O(N)
8. sort O(N Log N)
9. forEach / map / filter / reduce O(N)

What is SQL JOINS..!

EmanSaeed331 — Tue, 09 Aug 2022 00:09:08 +0000

JOINS TYPE ON SQL

LEFT JOIN
RIGHT JOIN
OUTER JOIN
INNER JOIN

How to make a CRUD operation By Nodejs and TypeScript .?

EmanSaeed331 — Mon, 08 Aug 2022 05:01:00 +0000

you can use a generic way to be applicable for any model you need, only you pass model and data type, and you can apply all crud operations on it.
source github

CREATE

   async function create<T>(data:T , model:any){
        const newObj = await new model(data);
        await newObj.save()
        return newObj;

READ

    async function read(model:any){
        return await model.find({});
    }

UPDATE


    async function update<T>(id:string, data:T , model:any){
        return  await model.findByIdAndUpdate(id,data); 
    }

DELETE

   async function getById (id:string,model:any){
        const data = await model.findOne({id});
        if(!data) {
            return 'id is not valid';
        }
        return data ; 
    }