const promise = new Promise((res,rej)=>{ if(true) res("it's pass"); else rej("there re error!!!"); }) promise .then(res=>res+"!!!") .then(res1=>{ console.log(res1); }) .catch(console.log("error for then 1 and 2")) .then(res3=>{ throw Error; console.log(res3); }) .catch(()=>console.log("error for then 3")) const promise1 = new Promise( (res,rej) => { setTimeout(res,100,"first") } ); const promise2 = new Promise( (res,rej) => { setTimeout(res,1000,"SECOND") } ); const promise3 = new Promise( (res,rej) => { setTimeout(res,2000,"THIRD") } ); Promise.all([promise,promise1,promise2,promise3]) .then((res)=> console.log(res)) .catch((err)=>console.log(err)); const url = [ "https://jsonplaceholder.typicode.com/posts", "https://jsonplaceholder.typicode.com/users", "https://jsonplaceholder.typicode.com/albums" ] Promise.all( url.map(url=>{ return fetch(url).then(res=>res.json()); }) ) .then( res=>{ console.log(res[0]); console.log(res[1]); console.log(res[2]) } );