Synchronous ,Asynchronous , Promise in JS

Synchronous JavaScript : Code runs line by line, and each line waits for the previous one to finish. console . log ( " First " ); console . log ( " Second " ); console . log ( " Third " ); Output : First Second Third If a single line of code takes a long time (like a huge loop or a complex calculation), it blocks the rest of the program from running. function slowTask (){ for ( let i = 1 ; i 999999999 ; i ++ ){ } } console . log ( " First " ); slowTask (); console . log ( " Third " ); Output : F