GCA

這次ECMA TC39 技術委員在Github上通過了ECMAScript語言特性的草案 詳情可以看這個  https://github.com/tc39/proposal-class-fields class的private property將可以用 # 來表示 現在 如果class要使用private property的話，必須利用Symbol或是WeakMap特性或是其他方法來實作 var _action = Symbol ( 'action' ) ; class Person { getXXX ( ) { return this [ _action ] ( ) ; } [ _action ] ( ) { return 'hi' ; } } 未來 而現在更新之後，直接偷範例過來用 class Counter extends HTMLElement { #xValue = 0 ; get # x ( ) { return #xValue ; } set # x ( value ) { this . #xValue = value ; window . requestAnimationFrame ( this . #render . bind ( this ) ) ; } # clicked ( ) { this . #x ++ ; } constructor ( ) { super ( ) ; this . onclick = this . #clicked . bind ( this ) ; } connectedCallback ( ) { this . # render ( ) ; } # render ( ) { this . textContent = this . #x . toString ( ) ; } } window . cus

前情提要 PEP 572是python 3.8 中的一個feature (Assignment Expressions) 而這個Assignment Expressions語法在最近掀起了Python生態的腥風血雨，先說明一下這是什麼改動 首先先貼一下PEP 572當中的介紹 In most contexts where arbitrary Python expressions can be used, a named expression can appear. This is of the form NAME := expr where expr is any valid Python expression other than an unparenthesized tuple, and NAME is an identifier.  以下是範例 if (match := pattern.search(data)) is not None: # Do something with match # A loop that can't be trivially rewritten using 2-arg iter() while chunk := file.read(8192): process(chunk) # Reuse a value that's expensive to compute [y := f(x), y**2, y**3] 而這個用法並沒有限制變數的位置，如下 def foo(answer = p := 42): # INVALID ... def foo(answer=(p := 42)): # Valid, though not great style ... 所以 當然也可以這樣 def foo(answer: p := 42 = 5): # INVALID ... def foo(answer: (p := 42) = 5): # Valid, but probably never useful 開了這個洞給程式碼，一定會有非常恐怖的程式碼出現 如同以下的程式碼，我們已經可以預測未來不久就會有這種寫法誕生在各個proje