var promise = new Promise(function(resolve, reject) {
// do some long running async thing…
if (/* everything turned out fine */) {
resolve("Stuff worked!");
}
else {
reject(Error("It broke"));
}
});
//usage
promise.then(
function(result) { /* handle a successful result */ },
function(error) { /* handle an error */ }
);console.log('some piece of code');
examplePromise.then(function(result){
console.log(result);
}).catch(function (error) {
console.error(error);
});
console.log('another piece of code');let promise = new Promise((resolve,reject)=>{
try {
resolve("some data");
} catch (error) {
reject(error);
}
})
promise.then(function (data) {
console.log(data);
},function (error) {
console.error(error);
})const count = true;
let countValue = new Promise(function (resolve, reject) {
if (count) {
resolve("There is a count value.");
} else {
reject("There is no count value");
}
});
console.log(countValue);Promises are used to handle asynchronous operations in JavaScript.
They are easy to manage when dealing with multiple asynchronous operations
where callbacks can create callback hell leading to unmanageable code.Promises make async javascript easier as they are easy to use and write than callbacks. Basically , promise is just an object , that gives us either success of async opertion or failue of async operations