Examples of synchronous and asynchronous code in JS

1. Using Synchronous

The program waits for the current task to finish before starting the next task

// code

console.log('start');

function run() {

console.log('before');

setTimeout(function() {console.log('wait 3 seconds')}, 3000);

console.log('after');

}

run();

console.log('end');

output

start

before

after

end

wait 3 seconds

2. Using Asynchronous 

The program can continue to execute while waiting for a task to complete

// code 

console.log('start');

async function run() {

console.log('before');

await setTimeout(function() {console.log('wait 3 seconds')}, 3000);

console.log('after');

}

run();

console.log('end');

output

start

before

end

after

wait 3 seconds

Thank you