function and contains one or more yield statements. The effect is to

return a value and pause execution at the current state. Declaring an

generator function returns an iterator. Subsequent calls to

iterator.next() resumes execution until the next yield. When the

iterator returns without using a yield statement there are no more

values and the done property of the iterator is set to true.cite-ref-21[21]

With the exception of iOS devices from Apple, generators are not

implemented for browsers on mobile devices. cite-ref-22[22]

function* generator() {

yield "red";

yield "green";

yield "blue";

}

let iterator=generator();

let current;

while(current=iterator.next().value)

console.log(current); //displays red, green then blue

console.log(iterator.next().done) //displays true

The await operator in JavaScript can only be used from inside an async

function or at the top level of a module. If the parameter is a promise,

execution of the async function will resume when the promise is resolved

(unless the promise is rejected, in which case an error will be thrown

that can be handled with normal JavaScript exception handling). If the

parameter is not a promise, the parameter itself will be returned

immediately.cite-ref-23[23]

Many libraries provide promise objects that can also be used with await,

as long as they match the specification for native JavaScript promises.

However, promises from the jQuery library were not Promises/A+

compatible until jQuery 3.0.cite-ref-24[24]

Below is an example (modified from thiscite-ref-async-await-javascript-async-await-25-0[25] article):

async function createNewDoc() {

let response = await db.post({}); // post a new doc

return db.get(response.id); // find by id

}

async function main() {

try {