如何从Javascript中的文件名字符串中提取扩展名？ [英] How to extract extension from filename string in Javascript?

问题描述

如何在变量中获取文件的File扩展名？
就好像我有一个文件 1.txt 我需要 txt 部分。

how would i get the File extension of the file in a variable? like if I have a file as 1.txt I need the txt part of it.

推荐答案

适用于以下所有输入的变体：

A variant that works with all of the following inputs:

• file.name.with.dots.txt


• file.txt


• file




• null


• undefined

• "file.name.with.dots.txt"
• "file.txt"
• "file"
• ""
• null
• undefined

将是：

var re = /(?:\.([^.]+))?$/;

var ext = re.exec("file.name.with.dots.txt")[1];   // "txt"
var ext = re.exec("file.txt")[1];                  // "txt"
var ext = re.exec("file")[1];                      // undefined
var ext = re.exec("")[1];                          // undefined
var ext = re.exec(null)[1];                        // undefined
var ext = re.exec(undefined)[1];                   // undefined

解释

(?:         # begin non-capturing group
  \.        #   a dot
  (         #   begin capturing group (captures the actual extension)
    [^.]+   #     anything except a dot, multiple times
  )         #   end capturing group
)?          # end non-capturing group, make it optional
$           # anchor to the end of the string

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