Asynchronous programming in JS:
Synchronous
- Stops execution of further code until this is done.
- Because it this stoppage of further execution, synchronous code is called 'blocking'. Blocking in the sense that no other code will be executed.
Asynchronous
- Execution of this is deferred to the event loop, this is a construct in a JS virtual machine which executes asynchronous functions (after the stack of synchronous functions is empty).
- Asynchronous code is called non blocking because it doesn't block further code from running.
Example:
// This function is synchronousfunction log(arg) { console.log(arg)}log(1);// This function is asynchronoussetTimeout(() => { console.log(2)}, 0);log(3)- The example logs 1, 3, 2.
- 2 is logged last because it is inside a asynchronous function which is executed after the stack is empty.