问题
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!
回答1:
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 Mac 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
回答2:
I believe this will work
searchText.replace(/(^[ \t]*\n)/gm, "")
回答3:
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.
来源：https://stackoverflow.com/questions/16369642/javascript-how-to-use-a-regular-expression-to-remove-blank-lines-from-a-string