DEV Community: Badri

React - Combining useMemo and Switch

Badri — Wed, 08 Sep 2021 05:43:52 +0000

useMemo is a react hook that gets executed only if any of the dependency changes. We can make it work like a switch by returning an object whose key will be the switch expression.

const Form = () => {
    switch(selectedUser){
        case "Admin" : return AdminForm;
                       break;
        case "User" : return UserForm;
                      break;
    }
}
//*AdminForm and UserForm are functional components

//This code is equivalent to 
const Form = useMemo(()=>{
   return { 
      "Admin" : AdminForm,
      "User" : UserForm,
   }[selectedUser];
},[selectedUser]);

/*
Breaking this down, if selectedUser is "Admin", we would return 
   { 
     "Admin" : AdminForm,
     "User" : UserForm,
   }["Admin"];
which is AdminForm.
*/

Here, Form gets executed only when selectedUser changes, so the expression need not be evaluated every time. This method allows us to optimise the expression evaluation as switch needs to execute it every time but useMemo doesn't.

How to see git history in VsCode?

Badri — Thu, 08 Jul 2021 19:05:20 +0000

Git History
Git History helps to view history and compare current code with previous commits.
Git Graph
Git Graph helps in visualising the repository and understanding the connection between the branches.

How to commit minor changes into a previous commit (changing history of repo)?

Badri — Thu, 08 Jul 2021 18:41:01 +0000

If you have a minor change for which you don't want to create a new commit. Use

git commit --amend --no-edit

This will allow you to create a new commit but replace the older one. But it will appear as if the old commit was never created. If you need to give a new message use -m flag to give a new message.

How to remove files from git?

Badri — Thu, 08 Jul 2021 18:37:34 +0000

git rm filename

If you need to remove a file from git but not from local repository. Use

git rm --cached filename

Do not forget to add the file to .gitignore if that file would be created again.

How to revert local branch to the remote branch commit?

Badri — Wed, 07 Jul 2021 11:04:44 +0000

git reset --hard origin/upstream_branch_name

This replaces the local branch with remote branch.