How-to: JavaScript trim() and normalize-space() functions

[Alex Vassiliev]

Hi all.

Just wanted to share two handy RegEx expressions to strips leading and
trailing white-space from a string, and to replace all repeated spaces,
newlines and tabs with a single space.

* JavaScript example:

String.prototype.trim = function() {
// Strip leading and trailing white-space
return this.replace(/^\s*|\s*$/g, "");
}

String.prototype.normalize_space = function() {
// Replace repeated spaces, newlines and tabs with a single space
return this.replace(/^\s*|\s(?=\s)|\s*$/g, "");
}

" one \t two three \n ".trim(); // --> "one \t two three"
" one \t two three \n ".normalize_space(); // --> "one two three"
Enjoy,
Alex Vassiliev (New Zealand)

[commercial]

you will not even get there on an OS handling basis
-----------

you are a lonely motherf*er

"Alex Vassiliev" <al************@gmail.com> wrote in message
news:11**********************@g47g2000cwa.googlegr oups.com...

Hi all.

Just wanted to share two handy RegEx expressions to strips leading and
trailing white-space from a string, and to replace all repeated spaces,
newlines and tabs with a single space.

* JavaScript example:

String.prototype.trim = function() {
// Strip leading and trailing white-space
return this.replace(/^\s*|\s*$/g, "");
}

String.prototype.normalize_space = function() {
// Replace repeated spaces, newlines and tabs with a single space
return this.replace(/^\s*|\s(?=\s)|\s*$/g, "");
}

" one \t two three \n ".trim(); // --> "one \t two three"
" one \t two three \n ".normalize_space(); // --> "one two three"
Enjoy,
Alex Vassiliev (New Zealand)

[Evertjan.]

Alex Vassiliev wrote on 29 sep 2005 in comp.lang.javascript:

String.prototype.trim = function() {
// Strip leading and trailing white-space
return this.replace(/^\s*|\s*$/g, "");
}

Nice one, Alex.

To have them all [the recurses are a variation]:

<script type='text/javascript'>

String.prototype.trim = function(x) {
if (x=='left')
return this.replace(/^\s*/,'');
if (x=='right')
return this.replace(/\s*$/,'');
if (x=='normalize')
return this.replace(/\s{2,}/g,' ').trim();

return this.trim('left').trim('right');
}

test = ' \n blah \n blah \n '
alert('x'+test+'x')
alert('x'+test.trim('left')+'x')
alert('x'+test.trim('right')+'x')
alert('x'+test.trim('both')+'x')
alert('x'+test.trim('normalize')+'x')
alert('x'+test.trim()+'x')

</script>

--
Evertjan.
The Netherlands.
(Replace all crosses with dots in my emailaddress)

[Michael Winter]

On 29/09/2005 09:08, commercial wrote:

[Corrected top-post]

"Alex Vassiliev" <al************@gmail.com> wrote in message
news:11**********************@g47g2000cwa.googlegr oups.com...
[snip]

String.prototype.trim = function() {
// Strip leading and trailing white-space
return this.replace(/^\s*|\s*$/g, "");
}
Incidentally, this already exists in the group FAQ
(<URL:http://www.jibbering.com/faq/#FAQ4_16>).
String.prototype.normalize_space = function() {
// Replace repeated spaces, newlines and tabs with a single space
return this.replace(/^\s*|\s(?=\s)|\s*$/g, "");
}

Useful as they are, lookahead assertions aren't available in all
browsers. Unless you're happy compromising execution by raising syntax
errors, they should be avoided:

String.prototype.normalise = function() {
return this.replace(/^\s+|\s+$/g, '').replace(/\s{2,}/g, ' ');
};

One thing that needs consideration is behaviour with mixed whitespace.
Your regular expression saves the last whitespace character in a
sequence. So, an earlier character could have been a new line, but might
be replaced by a space. Conversely, the sequence could have been all
spaces with the exception of a final new line, and it's that character
that is saved.

By comparison, the alternative above would always replace a whitespace
sequence with a single space.

[snip]
you will not even get there on an OS handling basis
If you do insist on posting, will you at least make sense. And don't
top-post.
you are a lonely motherf*er

However, if you're going to behave like that, could you refrain from
posting at all.

Mike

--
Michael Winter
Prefix subject with [News] before replying by e-mail.

[Alex Vassiliev]

>One thing that needs consideration is behaviour with mixed whitespace.

Your regular expression saves the last whitespace character in a
sequence. So, an earlier character could have been a new line, but might
be replaced by a space. Conversely, the sequence could have been all
spaces with the exception of a final new line, and it's that character
that is saved.

Good one! I haven't thought about that... It is definitely a bug.
Thank you Michael

[Dr John Stockton]

JRS: In article <11**********************@g47g2000cwa.googlegroups .com>
, dated Wed, 28 Sep 2005 18:28:42, seen in news:comp.lang.javascript,
Alex Vassiliev <al************@gmail.com> posted :

String.prototype.normalize_space = function() {
// Replace repeated spaces, newlines and tabs with a single
space
return this.replace(/^\s*|\s(?=\s)|\s*$/g, "");
}

That won't work for me.

Otherwise, I might have used it in my presently-crude paragraph-packer.

I much dislike reading articles,
usually
press statements or similar, in
which the
layout is like this forced
example
(but wider).

So I added a "Pack" button to <URL:http://www.merlyn.demon.co.uk/js-
quick.htm>; its code is still crude.

--
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