如何使用javascript发出异步请求以同步请求

Question

 function abc() {
    console.log(0)
    console.log(1)
 setTimeout(() => {
        console.log(2)
    },0)
    console.log(3)
}
abc()

I know this is async request how can i make it to sync. Can anyone help me on this please output should be 0,1,2,3

Answer 1

In javascript there are three ways to handle asynchronous calls, callbacks (deprecated) , Promises (only when you must) and async/await (recommanded) .

Using async/await

 function asyncFunction() { return new Promise((resolve) => { setTimeout(() => { console.log(2); resolve(); }, 0); }); } async function abc() { console.log(0); console.log(1); await asyncFunction(); console.log(3); } abc();

Using Promises

 function asyncFunction() { return new Promise((resolve) => { setTimeout(() => { console.log(2); resolve(); }, 0); }); } function abc() { return new Promise((resolve) => { console.log(0); console.log(1); asyncFunction() .then(() => { console.log(3); resolve(); }); }); } abc();

There are tons of tutorials online explaining what theses are and how to use properly.

Answer 2

Try this

 async function abc() { console.log(0) console.log(1) await setTimeout(() => { return Promise.resolve(1); }, 0) console.log(3) } abc().then(console.log(2))