Merge branch 'master' of https://github.com/KieSun/Front-End-Interview-Map

Author: YuChengKai

Framework/framework-zh.md

@@ -0,0 +1,8 @@
+# VDOM
+
+
+
+- 节点不一样就直接干掉
+- 相同的节点，先对比属性
+- 对于子节点，需要用 key 告诉我怎么复用，否则就按照上面的方式判断
+

JS/JS-ch.md

@@ -1361,6 +1361,28 @@ test()
 
 `async 和 await` 相比直接使用 `Promise` 来说，优势在于处理 `then` 的调用链，能够更清晰准确的写出代码。缺点在于滥用 `await` 可能会导致性能问题，因为 `await` 会阻塞代码，也许之后的异步代码并不依赖于前者，但仍然需要等待前者完成，导致代码失去了并发性。
 
+下面来看一个使用 `await` 的代码。
+
+```js
+var a = 0
+var b = async () => {
+  a = a + await 10
+  console.log('2', a) // -> '2' 10
+  a = (await 10) + a
+  console.log('3', a) // -> '3' 20
+}
+b()
+a++
+console.log('1', a) // -> '1' 1
+```
+
+对于以上代码你可能会有疑惑，这里说明下原理
+
+- 首先函数 `b` 先执行，在执行到 `await 10` 之前变量 `a` 还是 0，因为在 `await` 内部实现了 `generators` ，`generators` 会保留堆栈中东西，所以这时候 `a = 0` 被保存了下来
+- 因为 `await` 是异步操作，所以会先执行 `console.log('1', a)`
+- 这时候同步代码执行完毕，开始执行异步代码，将保存下来的值拿出来使用，这时候 `a = 10`
+- 然后后面就是常规执行代码了
+
 # Proxy
 
 Proxy 是 ES6 中新增的功能，可以用来自定义对象中的操作

JS/JS-en.md

@@ -973,3 +973,25 @@ test()
 The above code will print `finish` before printing `object`. Because `await` waits for the `sleep` function `resolve`, even if the synchronization code is followed, synchronization code is not executed before the asynchronization code is executed.
 
 The advantage of `async` and `await` compared to the direct use of `Promise` lies in handling the call chain of `then`, which can write code more clearly and accurately. The downside is that misuse of `await` can cause performance problems because `await` blocks the code. Perhaps the asynchronous code does not depend on the former, but it still needs to wait for the former to complete, causing the code to lose concurrency.
+
+Let's look at a code that uses `await`.
+
+```js
+var a = 0
+var b = async () => {
+  a = a + await 10
+  console.log('2', a) // -> '2' 10
+  a = (await 10) + a
+  console.log('3', a) // -> '3' 20
+}
+b()
+a++
+console.log('1', a) // -> '1' 1
+```
+
+You may have doubts about the above code, here explain the principle
+
+- First the function `b` is executed. The variable `a` is still 0 before execution  `await 10`, Because the `generators` are implemented inside `await` and  `Generators` will keep things in the stack, so at this time `a = 0` is saved
+- Because `await` is an asynchronous operation, `console.log('1', a)` will be executed first.
+- At this point, the synchronization code is executed and asynchronous code is started. The saved value is used. At this time, `a = 10`
+- Then comes the usual code execution