密碼至少包含 1 個大寫 1 個小寫 1 個數字 1 個特殊字元，長度至少為 10

由於字元/數字可以在字串中的任何位置，我們需要前瞻。前瞻是 zero width 意味著他們不消耗任何字串。簡單來說，在每個先行條件滿足後，檢查的位置重置到原始位置。

假設 ： - 將非單詞字元視為特殊字元

^(?=.{10,}$)(?=.*[a-z])(?=.*[A-Z])(?=.*[0-9])(?=.*\W).*$

在繼續解釋之前，讓我們來看看字串 1$d%aA 上的正規表示式如何工作（ 這裡不考慮長度 ）

圖片來源 ： - https://regex101.com/

值得注意的事情

• 由於錨標記^，從字串的開頭開始檢查。
• 在前瞻條件滿足後，檢查位置被重置為啟動。

正規表示式細分

^ #Starting of string
 (?=.{10,}$) #Check there is at least 10 characters in the string. 
             #As this is lookahead the position of checking will reset to starting again
 (?=.*[a-z]) #Check if there is at least one lowercase in string.
             #As this is lookahead the position of checking will reset to starting again
 (?=.*[A-Z]) #Check if there is at least one uppercase in string.
             #As this is lookahead the position of checking will reset to starting again
 (?=.*[0-9]) #Check if there is at least one digit in string.
             #As this is lookahead the position of checking will reset to starting again
 (?=.*\W) #Check if there is at least one special character in string.
          #As this is lookahead the position of checking will reset to starting again
.*$ #Capture the entire string if all the condition of lookahead is met. This is not required if only validation is needed

我們也可以使用上面的正規表示式的非貪婪版本

^(?=.{10,}$)(?=.*?[a-z])(?=.*?[A-Z])(?=.*?[0-9])(?=.*?\W).*$