javascript正则表达式 - 删除注释

Question

The example is from eloquent javascript book.Although There's a little explanation in the book it's really hard to follow, can anyone explain it from beginner perspective.I am having hard time to follow which slash is for what.

function stripComments(code) {
  return code.replace(/\/\/.*|\/\*[^]*\*\//g, "");
}

Answer 1

Comment can have two forms:

// this is a comment
/* this is a comment */

Unfortunately, both / and * are special characters in regular expressions, so they must be escaped.

So we start with an empty match expression

//g

We set it to match the first form, // followed by any number of characters, which would be //.* but the slashes have to be escaped

/\/\/.*/g

The other form, /* followed by anything followed by */ is /*[^]**/ but we have to escape the literal slashes and asterisks

\/\*[^]*\*\/

The two forms are then combined with a | character which denotes a "or":

\/\/.*|\/\*[^]*\*\/

and inserted into the empty regex

/\/\/.*|\/\*[^]*\*\//g

Answer 2

First and last slashes are delimiters.

g at the end is a modifier (Modifiers are used to perform case-insensitive and global searches) and performs a global match (find all matches rather than stopping after the first match).

| means OR .

\\/\\/.* has some escaped chars and can be translated as // followed by any characters \\/\\*[^]*\\*\\/ has also some escaped chars and can be translated as /*any characters*/

Note : both / and * must be escaped because they are used by regex syntax (special characters). So \\/ means / and \\* means * while .* means any characters (0 or more times)

Since the goal of your code is to remove comments, all comments like // xxxx or /* xxx */ are replaced by empty string

Answer 3

/ --> start of regex

/ --> escaped "/" character

/ --> escaped "/" character

.* --> any character (even empty) --> here is the case // abck

| --> OR

/ --> escaped "/" character

* --> escaped "*" character

[^]* --> any character (multiline, so even \\n\\r)

* --> escaped "*" character

/ --> escaped "/" character --> here is the case /* aasd\\nasdasd */

/ --> end of regex

g --> global modifier

Answer 4

Let's break it down with one token per line:

/    # Start a new regex

# This group of tokens matches comments in the form:
# // this is a comment

\/   # An escaped forward slash
\/   # An escaped forward slash
.*   # Any character, zero or more times

|    # OR. This means "match either the previous or the next group of tokens".

# This group of tokens matches comments in the form:
# /* 
#  This is a comment, which could include some new lines
# */

\/   # An escaped forward dlash
\*   # An escaped asterisk
[^]* # A newline, zero or more times
\*   # An escaped asterisk
\/   # An escaped forward slash

/    # Finish the current regex.
g    # This regex can match multiple times against a given input