Javascript validation, where string is compiled of only any number of spaces

Question

I am looking for a function that will return true / false if the string in question is complied of any number of spaces. The common method of doing this is if (string == " ") but this only works for one space. I need a function that would resolve any number of spaces to a return statement.

example

if (string == " ")
if (string == "  ")
if (string == "   ")
if (string == "    ")
if (string == "     ")

What is the best way to do this?

Does it need to be only spaces or would this string return true: string = " J " — Soatl
– Soatl, Commented Jul 14, 2011 at 20:57

Erik · Accepted Answer · 2011-07-14 20:56:45Z

3

You could use a simple regular expression:

var x = "    ";
if (x.match(/^ +$/)) {
  alert("yes");
} else {
  alert("no");
}

answered Jul 14, 2011 at 20:56

Erik

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3 Comments

nwellcome Over a year ago

To break that regex down for you: "^" matches the beginning of the string, " +" matches one or more space, "$" matches the end of the string.

nnnnnn Over a year ago

Your way works, of course, but if you just want a true/false matches/doesn't result I'd use .test().

Erik Over a year ago

Yes, .test() should be slightly faster

Tikhon Jelvis · Accepted Answer · 2011-07-14 21:05:52Z

2

You can use a regular expression: /^ +$/.test(string).

A regular expression is also good if you want to match any whitespace rather than just spaces (which is sometimes useful): /^\s+$/.test(string). The \s matches all whitespace characters like " " and "\t". So:

/^ +$/.test("     ");// True
/^ +$/.test("   \t\t");// False
/^\s+$/.test("      ");// True
/^\s+$/.test("    \t\t");// True

For reference, "\t" will look something like

"   "

(I think SO turned the tab into spaces, but that's more or less what it would look like.)

edited Jul 14, 2011 at 21:05

answered Jul 14, 2011 at 20:57

Tikhon Jelvis

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Comments

az4dan · Accepted Answer · 2011-07-14 20:57:36Z

1

function check(str)
{
    for (var i = 0; i < str.length; i++)
    {
        if (str[i] != " ") return false;
    }
    return true;
}

answered Jul 14, 2011 at 20:57

az4dan

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1 Comment

Tikhon Jelvis Over a year ago

I think that the str[i] syntax does not work under older versions of IE; consider using str.charAt(i) instead.

ChristopheCVB · Accepted Answer · 2011-07-14 20:59:48Z

1

Try :

String.prototype.count=function(s1) {
    return (this.length - this.replace(new RegExp(s1,"g"), '').length) / s1.length;
}
myString.length == myString.count(' ');

answered Jul 14, 2011 at 20:59

ChristopheCVB

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