1.promise对象

// promise对象
const promise=new Promise((resolve,reject)=>{console.log(1);resolve();console.log(2);
})
promise.then(()=>{console.log(3);
})
console.log(4);//打印的结果：1,2,4,3const promise=Promise.resolve(1).then(2).then(Promise.resolve(3)).then(console.log);
// 链式调用，then的参数是非函数，跳过。所以最终返回1。
// promise的应用
// 3秒之后亮一次红灯，再过两秒亮一次绿灯，再过1秒亮一次黄灯，用promise实现多次交替亮灯的效果
// 拆解：(1)多少秒后亮某个颜色的灯，(2)顺序亮一批灯，循环顺序亮一批灯
function light(color, second) {return new Promise(function (resolve, reject) {setTimeout(function () {console.log(color);resolve();}, second * 1000);})
}
function orderLights(list) {let promise = Promise.resolve();list.forEach(item => {promise = promise.then(function () {return light(item.color, item.second);})});promise.then(function () {return orderLights(list);})
}
orderLights([{color: 'red',second: 3,
}, {color: 'green',second: 2,
}, {color: 'yellow',second: 1,
}]);

2.generator函数

// generator函数 一个进程多个协程；
function* createIterator() {let first = yield 1;let second = yield first + 2;yield second + 3;
}let iterator = createIterator();
console.log(iterator.next());//返回yield 后面表达式的值
console.log(iterator.next(4));// 参数改变上一个yield后面表达式的值
console.log(iterator.next(5));
console.log(iterator.next());

3.async函数

// async函数
async function async1() {console.log("async1 start");await async2();console.log("async1 end");
}
async function async2() {return Promise.resolve().then(() => {console.log("async2 promise");})
}
async1();async function f() {await Promise.reject('error');//await 后是reject，后序代码不会执行console.log(1);await 100;
}// 后序代码执行，加try...catch
async function f() {await Promise.reject('error').catch(() => { });console.log(1);await 100;
}async function f() {try {await Promise.reject('error');} catch (e) {} finally {}console.log(1);await 100;
}f();