Regex to remove whitespaces

Question

I'm trying to write a regular expression to remove white spaces from just the beginning of the word, not after, and only a single space after the word.

This is the regex that I've tried:

var re = new RegExp(/^([a-zA-Z0-9]+\s?)*$/);
Output - 
re.test("")
true - required false
re.test(" ")
false
re.test(" word")
false - required word - true 
re.test(" word ")
false - required word - true 
re.test("word ")
true
re.test("word  ")
false - - required word(with single space ) - true

Exp:

See, I have to send a request to backend where if

1) key term is ""(blank) no need to send the request. 
2) If key is " string" need to send the request. 
3) If user enter something like this "string    string" need to send the request. 
4) if user enter "string " need to send the request. 
5) if user enter string with a space need to send the request but at the moment he enter another space no need to send the request.

This thing i am trying to achieve using regular expression.

Elaborate the task more please. "to remove white spaces from beginning" while in your examples you don't use `replace()` but a `test()` — zerkms, May 24 '13 at 14:11
Are you trying to only remove one whitespace char after the word, and leave any other whitespace chars there, or are you trying to reduce more than one whitespace character at the end to be no more than one space? Or are you trying to assert that the word must simply have a single space at the end to match? — ajp15243, May 24 '13 at 14:17

anubhava · Answer 1 · 2013-05-24T14:44:20.863

2

I think following should take care of all the space replacements for you:

var str      = "   this is     my  string    ";
var replaced = str.replace(/^\s+|\s+$|\s+(?=\s)/g, "");
// repl = 'this is my string'

edited May 24 '13 at 14:44

answered May 24 '13 at 14:37

anubhava

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Another possibilities for above: `var replaced = str.replace(/\s{2,}/g, ' ').trim();` which replaces 2 or more white spaces with a single space, and trims the start/end white spaces. – erosman Apr 30 '14 at 07:22
Yes that will also work but requires 2 method calls. – anubhava Apr 30 '14 at 07:24

score 1 · Answer 2 · answered May 24 '13 at 14:15

1

This would fit your case:

var myString = "   this is my string    ";
myString = myString.replace(/^\s+/ig, "").replace(/\s+$/ig,"")+" ";
alert(myString);

Tinker: http://tinker.io/e488a/1

answered May 24 '13 at 14:15

Sébastien Renauld

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Could be factorized in `myString.replace(/^\s*(.*?)\s*$/, "$1 ");`. – sp00m May 24 '13 at 14:24
@Sebastien Renauld it will not work for me. With you example the space is removed from both side but I need to have a only one space in last. – Soarabh May 24 '13 at 15:44
@saorabh: look at line #2 of the code. See where I'm concatenating a space at the end? – Sébastien Renauld May 24 '13 at 15:46
@sp00m: http://jsperf.com/stack-concat-regex-qu . Mine does not cause the regex calls to go over the entire string - performance gain is visible. 11% faster. – Sébastien Renauld May 24 '13 at 15:49

bert · Answer 3 · 2013-05-24T14:22:48.073

0

// this should do what you want
var re = new RegExp(/^([a-zA-Z0-9]+\s?)+$/);

edited May 24 '13 at 14:22

answered May 24 '13 at 14:17

bert

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I just had a look at the tests... I don't know why you want the input "" to fail. – bert May 24 '13 at 14:20
Have you changed your mind? Look at your question - You want "saorabh " (with 2 blanks) to fail. – bert May 24 '13 at 20:20

score 0 · Answer 4 · answered Apr 30 '14 at 08:09

I think the word boundary perfectly suits for this. Try this regexp:

var myString = "   test    ";
myString = myString.replace(/\s+\b|\b\s/ig, "");
alert('"' + myString + '"');

The regexp removes all spaces before all words and the first space after all words

Regex to remove whitespaces

4 Answers4

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