Promise/a+部分实现

实现了部分的 Promise/a+ 规范.只用于学习理解使用, 所以只简单测过几个 case, 不可用于生产环境. 另外.catch, .finally, .all 等. 其实都很好实现, 类似于或者基于.then, 看一下明白了. .all() 稍微复杂一点, 但是也没有什么东西, 理解就完事了. 懒癌晚期

==> 等同于 下一步

• new Promise(fn) ==> call(fn), with resolve, reject arguments
• resolve(value) ==> resolve Promise value/resolve function value/resolve value
• and else promise.state = 1, iterate hander[], calling every handler, with promise.value
• then(handler), if pedding, push to handler[], else, before the next eventLoop, res = onFulfill(state.value)/onReject(state.value), and resolve the handler promise with res

Reference

• Promise/A+规范
• Promise-implementing
• github:then/promise