2023-02-16
轉換
首先,看如下JavaScript代碼
看到這里,你是否眼花繚亂,沒有頭緒呢?只用 []()!+ 這六個字符就可以實現一段可執行的 JavaScipt 代碼,這是如何實現的呢?
類型轉換
JavaScript 是弱類型的編程語言,我們在寫代碼的時候充斥著大量的類型轉換,如下表
根據數據類型轉換:
· !后的字符會被轉換為布爾值
//false
![]
//true
!![]
//undefined
[][[]]
//NaN
+[![]]
· +后的字符會被轉換為數值
//結果是什么呢?提示:[]被轉換為0
+[] === 0
//結果是什么呢?提示:[]被轉換為0,!0是true,+true是1
+!+[] === 1
//結果是什么呢?
[+!+[]] + [+[]]] === [1]+[0] === '10'
· +[] 前的字符會被轉換為字符串
//結果是什么呢?
!+[]+!+[] === 2
思考1
//1.提示:+[]被轉換為0,[][0]為undefined
[][ +[] ] === undefined
//2.提示:false +[]為'false',[+!![]]為1,所以結果為a——擴展后可以獲取到想要的字母
(false +[]) [+!![]] === 'a'
//3.提示:0["constructor"]為Number,Number+[]轉為字符串"function Number(){}"
0["constructor"]+[]
//4.提示:通過 []["find"] 可以拿到數組的 find 方法,find 方法的構造函數其實就是 Function
[]["find"]["constructor"] === Function
思考2
根據以上內容推導:
//1.表示f
(![]+[])[+[]]
//2.表示find
(![]+[])[+[]]+([![]]+[][[]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+([][[]]+[])[!+[]+!+[]]
//3.表示constructor
([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]
//4.表示alert
(![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]
//5.表示 []["find"]["constructor"]("alert(1)")():
[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]][([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+([][[]]+[])[+!+[]]+(![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[])[+!+[]]+([][[]]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+[]]+(!![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[+!+[]+[+[]]]+(!![]+[])[+!+[]]]((![]+[])[+!+[]]+(![]+[])[!+[]+!+[]]+(!![]+[])[!+[]+!+[]+!+[]]+(!![]+[])[+!+[]]+(!![]+[])[+[]]+([][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]]+[])[+!+[]+[!+[]+!+[]+!+[]]]+[+!+[]]+([+[]]+![]+[][(![]+[])[+[]]+(![]+[])[!+[]+!+[]]+(![]+[])[+!+[]]+(!![]+[])[+[]]])[!+[]+!+[]+[+[]]])()
你明白了嗎?
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