async - Promise

// Async Version
async function callAPIs(){
    return doSomething();
}

//Promise Version
function callAPIs(){
    return new Promise((resolve,reject)=>{
        resolve(doSomething());
    })
}

Async <-> Promise

// async function <-> new Promise Object
// await keyword <-> then() method call
// catch block <-> catch() method call
// return keyword <-> resolve() function call
// throw error <-> reject() function call
//

// Async Version 
async function callAPIs(){
    try{
        let res1 = await axios.get("http://example.com")
        let res2 = await axios.get(`http://example2.com?key1=${res1.key2}`)
        return res2.key2;
    }catch(err){
        console.log(err);
        throw err;
    }
}

// Promise version
function callAPIs(){
    return new Promise((resolve,reject)=>{
        axios.get("http://example.com")
            .then((res1)=>axios.get(`http://example2.com?key1=${res1.key2}`))
            .then((res2)=> resolve(res2.key2))
            .catch((err)=>{
                console.log(err);
                reject(err);
            });            
    });
}

await - then

//Async version
async function callAPIs(){
    let res1 = await axios.get("http://example.com")
    return res1;
}

// Promise version
function callAPIs(){
    return new Promise((resolve,reject)=>{
        axios.get('http://example.com')
            .then((res1)=>resolve(res1));
    });
}

Axios

// GET method
axios.get("/users")
    .then(res=> console.log(res))
    .catch(err=> console.log(err));

// POST method
axios.post("/users",{"id":2,"username":"newUserName"})
    .then(res=> console.log(res) )
    .catch(err=> console.log(err) );

// DELETE method
axios.delete("/users",{id:3})
    .then(res=> console.log(res))
    .catch(err=> console.log(err));

// PUT method
axios.put("/users",{"email":"user@user.com","password":"1234"})
    .then(res=> console.log(res))
    .catch(err=> console.log(res));

catch block - catch

// Async version
async function callAPIs(){
    try{
        let res1 = await axios.get('http://example.com');
        return res1;
    }catch(err){
        console.log(err);
        throw err;
    }
}

// Promised version
function callAPIs(){
    return new Promise((resolve,reject)=>{
        axios.get("http://example.com")
        .then((res1)=>resolve(res1))
        .catch((err)=> reject(err))
    });
}

Promise.all

// Async version

async function callAPIs(){
    let combinedPromise = Promise.all([axios.get('http://example1.com'),
                                        axios.get('http://example2.com')]);
    let responses = await combinedPromise;
    return responses;
}

// Promised version
const p1 = new Promise((resolve, reject) => {
  setTimeout(resolve, 1000, 'one');
});
const p2 = new Promise((resolve, reject) => {
  setTimeout(resolve, 2000, 'two');
});

Promise.all([p1, p2])
    .then(values => console.log(values))
    .catch(err => console.log(err));