JavaScript Promise examples

promise.js

<script>

function getSalary(salary) {
	return new Promise(resolve => {
		setTimeout(() => {
			resolve(salary);
		}, 500);
	});
}

function errorSalary() {
	throw 'Wrong salary';
}

function reduceBill(salary) {
	return new Promise(resolve => {
		setTimeout(() => {
			resolve(salary - 100);
		}, 500);
	});
}

function reduceTax(salary) {
	return new Promise(resolve => {
		setTimeout(() => {
			resolve(salary - 100);
		}, 500);
	});
}

function getSum() {
	return Promise.all([
		getSalary(1000),
		getSalary(2000),
		getSalary(3000),
	]).then(salaries => {
		return salaries.reduce((prev, cur) => prev + cur, 0);
	});
}

getSalary(1000)
	.then(salary => reduceBill(salary))
	.then(errorSalary)
	.then(salary => reduceTax(salary))
	.then(salary => console.log(salary))
	.catch(e => console.log('EE' + e));

</script>