How Promise.all works

Promise.all waits till all the promises passed to it are resolved. Here is an example code snippet:

async function fun1() {

console.log("1 before wait");

return new Promise((resolve, reject) => {

setTimeout(() => {

console.log("1 after wait");

resolve();

}, 3000);

});

}

async function fun2() {

console.log("2 before wait");

return new Promise((resolve, reject) => {

return setTimeout(() => {

console.log("2 after wait");

resolve();

}, 2000);

});

}

async function main() {

console.log("start");

await Promise.all([fun1(), fun2()]);

console.log("end");

}

main();

The above snippet outputs

start
1 before wait
2 before wait
2 after wait
1 after wait
end