Javascript check for spaces

Question

I have this function but I want to check for spaces only in the front and back, not in the middle before i sent back what can i do with it...

function validateNumeric() {
  var val = document.getElementById("tbNumber").value;
  var validChars = '0123456789.'; 

  for(var i = 0; i < val.length; i++){ 
    if(validChars.indexOf(val.charAt(i)) == -1){
    alert('Please enter valid number');
    return false; 
    } 
  }
  return true; 
  }

What does checking for leading/trailing spaces have to do with checking to see if the input is a valid number? — Matt Ball, Jun 03 '11 at 14:07

Matt Ball · Answer 1 · 2011-06-03T15:19:23.997

12

Time for regular expressions.

function startsOrEndsWithWhitespace(str)
{
    return /^\s|\s$/.test(str);
}

Tests:

> /^\s|\s$/.test('123454')
  false
> /^\s|\s$/.test('123 454')
  false
> /^\s|\s$/.test(' 123454')
  true
> /^\s|\s$/.test(' 123454 ')
  true
> /^\s|\s$/.test('123454 ')
  true

if i dont wanna accept 1 1 what do i have to change

function containsWhitespace(str)
{
    return /\s/.test(str);
}

Tests:

> /\s/.test('123454')
  false
> /\s/.test('123 454')
  true
> /\s/.test(' 123454')
  true
> /\s/.test('123454 ')
  true
> /\s/.test(' 123454 ')
  true
> /\s/.test(' 123 454 ')
  true

edited Jun 03 '11 at 15:19

answered Jun 03 '11 at 14:01

Matt Ball

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... or `return /^\s|\s$/.test(str);` - à chacun son goût – Pointy Jun 03 '11 at 14:04
@jack Start at http://regexlib.com/DisplayPatterns.aspx?cattabindex=2&categoryId=3 for ideas :) – OnesimusUnbound Jun 03 '11 at 14:04
@Pointy already decided I prefer `re.test(string)` before I saw your comment `:)` – Matt Ball Jun 03 '11 at 14:06
This actually answers the badly formulated question. :J – Zecc Jun 03 '11 at 14:19
is it going to accept 1.1 coz i need to say ok to number with decimal – jack Jun 03 '11 at 15:26
@jack just how hard would it be to test that yourself? Allow me to introduce you to your browser's console: http://stackoverflow.com/questions/1648582/equivalent-of-firefoxs-error-console-in-other-browsers – Matt Ball Jun 03 '11 at 15:27
@jack I've create a [jsfiddle](http://jsfiddle.net/qDPeW/) for you to *try and edit* until you've solve the issue :-) – OnesimusUnbound Jun 03 '11 at 18:24

Mike Samuel · Answer 2 · 2011-06-03T23:31:58.910

function validateNumeric() {
  var val = document.getElementById("tbNumber").value;
  if (!/^\s*(?:\d+(?:\.\d*)?|\.\d+)\s*$/.test(val)) {
    alert('Please enter a valid number');
    return false; 
  }
  return true;
}

(?:\d+(?:\.\d*)|\.\d+) breaks down as follows:

\d+ is any number of digits, e.g. 123
(\.\d*)? optionally matches a fraction, e.g. .25 and . or blank but not .1.2
\.\d+ matches a fraction without an integer part as in .5 but not 1.5.
(?:abc|def) groups things together and matches either abc or def

/^\s*(?:\d+(?:\.\d*)|\.\d+)\s*$/ means any number of spaces followed by one or more decimal digits followed by any number of spaces. So it does what your validChars loop did plus allows spaces at the start and end.

score 0 · Answer 3 · answered Jun 03 '11 at 14:03

0

For a really simple solution, if you can use jQuery, use jQuery.trim() and compare the trimmed string with the original. If not equal, then there were spaces so the number is invalid.

answered Jun 03 '11 at 14:03

score 0 · Answer 4 · answered Jun 03 '11 at 14:04

0

function trim (myString)
{
return myString.replace(/^\s+/g,'').replace(/\s+$/g,'')
}

source

answered Jun 03 '11 at 14:04

Kraz

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"check for spaces" != "remove spaces" – Matt Ball Jun 03 '11 at 14:05

score 0 · Answer 5 · edited May 23 '17 at 12:04

To trim your string you can write something like this, as it's been said before:

function trim(str){
    return str.replace(/^\s+|\s+$/g), '');
}

But why bother?
Want you really want is:

function validateNumeric(str) {
    return !isNaN(parseFloat(str));
}

Note your original code accepts something like "..." or "7.8..9" as being numeric, which is wrong.

Update: kennebec has called my attention to the fact that parseFloat() will ignore trailing garbage at the end of string. So I call your attention to this alternative given in an answer to question "Validate numbers in JavaScript - IsNumeric()":

function isNumber(n) {
    return !isNaN(parseFloat(n)) && isFinite(n);
}

(Original credit goes to CMS).

This will accept input that starts with a number but can include anything after that. if(parseFloat(str)+''===str) would do. — kennebec, Jun 03 '11 at 15:58

Javascript check for spaces

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