How to remove all line breaks from a string

You can use \n in a regex for newlines, and \r for carriage returns.

var str2 = str.replace(/\n|\r/g, "");

Different operating systems use different line endings, with varying mixtures of \n and \r. This regex will replace them all.

var str = " \n this is a string \n \n \n"

console.log(str);
console.log(str.trim());

String.trim() removes whitespace from the beginning and end of strings... including newlines.

const myString = "   \n \n\n Hey! \n I'm a string!!!         \n\n";
const trimmedString = myString.trim();

console.log(trimmedString);
// outputs: "Hey! \n I'm a string!!!"

Here's an example fiddle: http://jsfiddle.net/BLs8u/

NOTE! it only trims the beginning and end of the string, not line breaks or whitespace in the middle of the string.

Line breaks (better: newlines) can be one of Carriage Return (CR, \r, on older Macs), Line Feed (LF, \n, on Unices incl. Linux) or CR followed by LF (\r\n, on WinDOS). (Contrary to another answer, this has nothing to do with character encoding.)

Therefore, the most efficient RegExp literal to match all variants is

/\r?\n|\r/

If you want to match all newlines in a string, use a global match,

/\r?\n|\r/g

respectively. Then proceed with the replace method as suggested in several other answers. (Probably you do not want to remove the newlines, but replace them with other whitespace, for example the space character, so that words remain intact.)

How you'd find a line break varies between operating system encodings. Windows would be \r\n, but Linux just uses \n and Apple uses \r.

I found this in JavaScript line breaks:

someText = someText.replace(/(\r\n|\n|\r)/gm, "");

That should remove all kinds of line breaks.