setTimeout(function () {
console.log(1);
}, 0)
new Promise(function executor(resolve) {
console.log(2);
for (var i = 0; i < 1000; i++) {
i = 9999 && resolve();
}
console.log(3);
}).then(function () {
console.log(4);
})
console.log(5);
输出结果：2 3 5 4 1