Re: [問題] Hoisting 問題

看板Ajax作者iamnodoubt (Have Fun)時間7年前 (2017/02/19 03:32)推噓6(6推 0噓 8→)

留言14則, 7人參與討論串2/3 (看更多)

※ 引述《broo (陳爺)》之銘言： : 標題: [問題] Hoisting 問題 : 時間: Sat Feb 18 23:48:05 2017 : 範例是這樣的 : (function(){ : var test =function(){return 1;} : function test() {return 2;} : return test(); : })(); : 經過hoistibg後會長這樣 : (function(){ : var test; : function test() {return 2;} : test = function() {return 1;} : return test(); : })(); : 我怎麼想結果都是2，因為最後是return test()不是嗎？？為什麼會是1呢 : 腦筋無法轉過來.. : 麻煩了手機排版請見諒我覺得hoisting應該不是這樣解釋 https://developer.mozilla.org/zh-TW/docs/Glossary/Hoisting hoisting teaches that variable and function declarations are physically moved to the top your coding, but this is not what happens at all. What does happen is the variable and function declarations are put into memory during the compile phase, but stays exactly where you typed it in your coding. 簡單講就是javascript會分creation跟execution phases 會先執行creation phases 把宣告的變數跟宣告的function存到記憶體 (此時變數還沒被assign,所以value會是undefined) 然後再執行excution phases 就是逐行的去執行程式碼 -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 61.231.184.212 ※ 文章網址: https://www.ptt.cc/bbs/Ajax/M.1487446363.A.C17.html

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lym520

02/19 08:52, , 1^F

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broo

02/19 10:04, , 2^F

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broo

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