这个正则表达式是什么：/ [\\ [] /？

Question

我很难理解这意味着什么： /[\\[]/为什么有两个替换语句？

name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");

Answer 1

/[\\[]/ is a regular expression literal .

In the first replacement, you're replacing a [ by \\[ and the symetric in the second one.

It looks weird because of many (mostly useless) escapements : [ is escaped in the regex and \\ and [ are escaped in the string literal.

The first regex can be analyzed like this :

• / : regex opening
• [ : character set opening
• \\[ : the [ character (with an escaping that is useless as it's in a set)
• ] : character set closing
• / : regex closing

Those regexes look too verbose to me : you don't need a character set if you have just one character in that set. And you don't need to escape the [ in the string literal.

You could have done

 name = name.replace(/\[/, "\\[").replace(/\]/, "\\]");

For example

 'a [ b c ] d [ e ]'.replace(/\[/, "\\[").replace(/\]/, "\\]")

gives

 "a \[ b c \] d [ e ]"

Note that as there is no g modifier, you're only doing one replacement in each call to replace , which probably isn't the goal, so you might want

 name = name.replace(/\[/g, "\\[").replace(/\]/g, "\\]");

Answer 2

That is using regular expression. If you are not familiar with regular expression, you may want to study that first.

Answer 3

This really isn't specific to Javascript, regular expressions are used in most programming languages with slight variations. Look into regular expressions, very useful once you know it!

Answer 4

Maybe you will see how it works on example

var name = "[[[[[]]]]]]]";
name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
console.log(name);

as result you will have

\[[[[[\]]]]]]] 

This regular expression replace first occurrence of [ to \\[ and first occurrence ] to \\]