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 Enter fullscreen mode Exit fullscreen mode 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 : First Third Enter fullscreen mode Exit fullscreen mode Asynchronous JavaScript : Asynchronous code allows a program to start a long-running task and continue with others before that task finishes. Code doesn't wait — it moves on and comes back when the task is done.So the page wouldn't freeze. Used in: Fetching data from an API. Reading a file Database queries Timers console . log ( " First " ); setTimeout (() => { console . log ( " Async task " ); }, 2000 ); console .…