promise resolve example
Example 1: promise resolve reject
function testFunction(value) {
return new Promise(function (resoleve, reject) {
setTimeout(function () {
let n = value;
if (n < 100) {
resoleve("範囲内");
} else {
reject("範囲外");
}
}, 2000);
})
}
testFunction(10)
.then(function (value) {
console.log(value);
return testFunction(50);
})
.then(function (value) {
console.log(value);
return testFunction(150);
})
.catch(function (error) {
console.log(`エラーです。${error}`);
})
Example 2: what is promise in javascript
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
Example 3: promise resolve reject
function testFunction() {
return new Promise(function (resolve, reject) {
setTimeout(function () {
resolve('hello!');
}, 1000);
})
}
testFunction()
.then(function (value) {
console.log(value);
})
.catch(function (error) {
console.log(error);
})
Example 4: Promise.resolve
var original = Promise.resolve(33);
original.then( val => console.log('origianl', val);
var cast = Promise.resolve(original);
cast.then(function(value) {
console.log('value: ' + value);
});
console.log('original === cast ? ' + (original === cast));