JavaScript: how to use a regular expression to remove blank lines from a string?
JavascriptRegexBlank LineJavascript Problem Overview
I need to use JavaScript to remove blank lines in a HTML text box. The blank lines can be at anywhere in the textarea
element. A blank line can be just a return or white spaces plus return.
I am expecting a regular expression solution to this. Here are some I tried, but they are not working and cannot figure out why:
/^\s*\r?\n/g
/^\s*\r?\n$/g
Edit 1
It appears that the solution (I modified it a little) suggested by aaronman and m.buettner works:
string.replace(/^\s*\n/gm, "")
Can someone tell why my first regular expression is not working?
Edit 2
After reading all useful answers, I came up with this:
/^[\s\t]*(\r\n|\n|\r)/gm
Is this going to be one that cover all situations?
Edit 3
This is the most concise one covering all spaces (white spaces, tabs) and platforms (Linux, Windows, Mac).
/^\s*[\r\n]/gm
Many thanks to m.buettner!
Javascript Solutions
Solution 1 - Javascript
Your pattern seems alright, you just need to include the multiline modifier m
, so that ^
and $
match line beginnings and endings as well:
/^\s*\n/gm
Without the m
, the anchors only match string-beginnings and endings.
Note that you miss out on UNIX-style line endings (only \r
). This would help in that case:
/^\s*[\r\n]/gm
Also note that (in both cases) you don't need to match the optional \r
in front of the \n
explicitly, because that is taken care of by \s*
.
As Dex pointed out in a comment, this will fail to clear the last line if it consists only of spaces (and there is no newline after it). A way to fix that would be to make the actual newline optional but include an end-of-line anchor before it. In this case you do have to match the line ending properly though:
/^\s*$(?:\r\n?|\n)/gm
Solution 2 - Javascript
I believe this will work
searchText.replace(/(^[ \t]*\n)/gm, "")
Solution 3 - Javascript
This should do the trick i think:
var el = document.getElementsByName("nameOfTextBox")[0];
el.value.replace(/(\r\n|\n|\r)/gm, "");
EDIT: Removes three types of line breaks.
Solution 4 - Javascript
Here's another solution:
string = string.replace(/^(?=\n)$|^\s*|\s*$|\n\n+/gm, "")
It appears to handle both blank lines and space-only lines.
Solution 5 - Javascript
function removeEmptyLine(text) {
return text.replace(/(\r?\n)\s*\1+/g, '$1');
}
test:
console.assert(removeEmptyLine('a\r\nb') === 'a\r\nb');
console.assert(removeEmptyLine('a\r\n\r\nb') === 'a\r\nb');
console.assert(removeEmptyLine('a\r\n \r\nb') === 'a\r\nb');
console.assert(removeEmptyLine('a\r\n \r\n \r\nb') === 'a\r\nb');
console.assert(removeEmptyLine('a\r\n \r\n 2\r\n \r\nb') === 'a\r\n 2\r\nb');
console.assert(removeEmptyLine('a\nb') === 'a\nb');
console.assert(removeEmptyLine('a\n\nb') === 'a\nb');
console.assert(removeEmptyLine('a\n \nb') === 'a\nb');
console.assert(removeEmptyLine('a\n \n \nb') === 'a\nb');
console.assert(removeEmptyLine('a\n \n2 \n \nb') === 'a\n2 \nb');