无法弄清楚此JS代码的含义

Question

I've been romping through a piece of JS I came across online and can't figure out what this piece of code means.

global$string$newLines = function(a) {
    return a.replace(/(\r\n|\r|\n)/g, "\n");
},

I'm specifically wondering about the piece /(\\r\\n|\\r|\\n)/g

Also - Is this machine generated code? Is that why the variable name is full of $s?

Answer 1

They are regular expresions

\r = Find a carriage return character
\n = Find a new line character

the /g (g only) mean to find all

http://www.w3schools.com/jsref/jsref_obj_regexp.asp

So the code mean to find all \\r\\n or just \\r or just \\n and replace it with \\n They are whitespace characters so they not visible.

Answer 2

It's a regular expression for replacing newline characters.

There are different types of new line characters inserted by various browsers/editors/OSes etc.

\\n is the default on all (true) Unix systems with \\r having no meaning, C, Java, C++, etc, adopted this convention.

\\r is from the days of Mac before it was a Unix system, while the duplicate \\r\\n is the Windows way.

The /g flag represents a global setting telling the regular expression to search the entire document.

So what the code is doing is using a regular expression to globally find all possible equivalents of a newLine, and replacing them with the defacto standard, '\\n'

Answer 3

This is just a regular expression used to replace Carriage Returns and New Line characters with new line characters.

Your Regex: /(\\r\\n|\\r|\\n)/g

Explanation:

1st Capturing group (\\r\\n|\\r|\\n)

1st Alternative: \\r\\n

\\r matches a carriage return (ASCII 13) \\n matches a line-feed (newline) character (ASCII 10)

2nd Alternative: \\r

\\r matches a carriage return (ASCII 13)

3rd Alternative: \\n

\\n matches a line-feed (newline) character (ASCII 10)

g modifier : global. Give All matches (ie Don't return on first match).

PS: Check out regex101.com for generating such beautiful explanation for any Regex.

Answer 4

The code replaces carriage-return/new-line combinations with a single newline.

The $'s in the variable name is done by several javascript compilers out there. Developers will often break their code up into namespaces of the form global.string.newline , for example. But when we want to run that code on a client, it's safer and more efficient to turn this object-within-an-object-within-an-object into a single variable. Usually, the javascript compiler will go one step further and then turn this long variable name into some short unique sequence, but it will also preserve this intermediate form for easier debugging.

Answer 5

It is a regex to remove the carriage return/new line/carriage return + new line with new line from a string.

/(\r\n|\r|\n)/g 

the /g in the end signifies globally, hence throughout the string and not just the first occurence.

Working Fiddle

JS Code:

global$string$newLines = function (a) {
    return a.replace(/(\r\n|\r|\n)/g, "\n")
}

function abc() {
    var text = document.getElementById("test").value;
    console.log(global$string$newLines(text));
}

HTML Code:

<textarea id="test"></textarea>
<button id="testClick" onclick="abc()">Click</button>

Answer 6

This is a regular expression replace that means:

Find any occurence of either:

• \\r\\n
• \\r
• \\n

And replace it with \\n.

Comments:

• The /g means it will mach all findings, not only the first occurence.
• The third option to replace \\n by \\n is nonsense as it has no effect.

Doc of the replace and link to regex: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace