Promise

Promise in JS got three states – resolve, reject and pending. Following example shows a reject state.

promise = new Promise((resolve, reject) => {
    reject();
});

promise
    .then(() => {console.log('finally finished')})
    .then(() => {console.log('i was also ran')})
    .catch(()=> {console.log('catch rejected')})

Output 
//catch rejected

Another example with resolve status

promise = new Promise((resolve, reject) => {
    resolve();
});

promise
    .then(() => {console.log('finally finished')})
    .then(() => {console.log('i was also ran')})
    .catch(()=> {console.log('catch rejected')})

//Output
finally finished
i was also ran

promise = new Promise((resolve, reject) => {
    setTimeout(() => {
        resolve();
    }, 3000);

});

promise
    .then(() => {
        console.log('finally finished')
    })
    .then(() => {
        console.log('i was also ran')
    })
    .catch(() => {
        console.log('catch rejected')
    })

//Output after 3 seconds. 
finally finished
i was also ran

Type the below in Chrome console and you will get the response in JSON format.

url = 'https://jsonplaceholder.typicode.com/posts';

fetch(url)
    .then(response =>response.json())
    .then(data =>console.log(data));