理解 Co 库的源码

Co 流程流程控制器源码与理解,index.js 包含理解和注释

简单版本的 Co 库

这个版本是重点是理解 generator 工作原理

// @flow
/**
 * Created by Freax on 16-12-12.
 * @Blog http://www.myfreax.com/
 */
function co(generator) {
    let gen = generator();
    next(gen.next()); //递归遍历 generator.next
    function next(result) {
        if (result.done)return null;//如果 generator 执行完毕，直接解决退出遍历
        let res = gen.next(result.value);
        next(res);
    }
}

co(function *gen() {
    let a = yield 1;
    console.info(a, 'a');
    let b = yield 2;
    console.info(b, 'b');
    let c = yield 3;
    console.info(c, 'c');
});

generator+promise Co 库的简版

理解 generator+promise 如何工作

// @flow
/**
 * Created by Freax on 16-12-12.
 * @Blog http://www.myfreax.com/
 */

function isPromise(obj) {
    return typeof obj === 'object' && 'function' == typeof obj.then;
}

function co(generator) {
    return new Promise((resolve,reject)=>{
        let gen = generator();
        next(gen.next());
        function next(result) {
            if (result.done)return resolve(result.value);//如果 generator 执行完毕，直接解决退出遍历
            //判断是否是 Promise ，如果是 promise 则执行 promise 再进入 next 递归遍历 generator.next
            if (isPromise(result.value))return result.value.then(res => {
                let result;
                try {
                    result = gen.next(res); //抛出 generator 的错误
                }catch (e){
                    return reject(e);// 捕获后由交给 promise 处理返回外部处理
                }
                next(result)
            }, err => {
                let result;
                try {
                    result = gen.throw(err); //yield 返回 promise 进入 reject 后的错误，抛出 generator 的错误
                }catch (e){
                    return reject(e); // 捕获后由交给 promise 处理返回外部处理
                }
                next(result)
            });
            let res = gen.next(result.value);
            next(res);
        }
    });

}

co(function *gen() {
    let a = yield Promise.resolve(1);
    console.info(a, 'a');
    let b = yield 2;
    console.info(b, 'b');
    let c = yield 3;
    console.info(c, 'c');

}).catch((err)=>{
    console.info(err);
});

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