例1
console.log('1');
async function async1() {
console.log('2');
await async2();
console.log('3');
}
async function async2() {
console.log('4');
}
process.nextTick(function() {
console.log('5');
})
setTimeout(function() {
console.log('6');
process.nextTick(function() {
console.log('7');
})
new Promise(function(resolve) {
console.log('8');
resolve();
}).then(function() {
console.log('9')
})
})
async1();
new Promise(function(resolve) {
console.log('10');
resolve();
}).then(function() {
console.log('11');
});
console.log('12');
//执行结果：1 2 4 10 12 5 11 3 6 8 7 9
注意：async函数会返回一个Promise，resolve()中的值为await后面表达式的值；遇到await，返回Promise之后，await后面的代码先不执行，直接跳出async函数
例2
async function async1() {
console.log('async1 start');
await async2();
console.log('async1 end');
}
async function async2() {
console.log('async2');
}
console.log('script start');
setTimeout(function() {
console.log('setTimeout');
}, 0)
async1();
new Promise(function(resolve) {
console.log('promise1');
resolve();
}).then(function() {
console.log('promise2');
});
console.log('script end');
/*
输出结果：
script start
async1 start
async2
promise1
script end
async1 end
promise2
setTimeout
*/