is this correct syntax in jquery/javascript?

Question

In the jquery below should there be a closing paretheses ")" before the "dot" in:

".test($ ..."?

(/^\s*$/.test($(this).val()))

$(document).ready(function () {
    $('#userlogin').css('color', '#cccccc').val('LOGINNAME');   

    $('#userlogin').blur(function () {
        if (/^\s*$/.test($(this).val())) {
            $(this).val('LOGINNAME');
            $(this).css('color', '#cccccc');
            $(this).valid();
        }
    }).focus(function () {
        if ($(this).val() === 'LOGINNAME') {
            $(this).val('');
            $(this).css('color', '#000000');
        }
    });

If not, why not? That code looks a little weird to me.

/something/ is a regular expression. In Javascript they are objects with methods, and test is one such method. There's nothing wrong with the code. — user1207456
– user1207456, Commented May 18, 2012 at 16:03
There is one more way to avoid confusion like this and that is proper code formatting with some whitespace to render the code les cryptic — user1115652
– user1115652, Commented May 18, 2012 at 22:04

ThiefMaster · Accepted Answer · 2012-05-18 16:02:03Z

4

The code is correct:

/^\s*$/  // create a regex
  .test( // call the test method on it
    $(this) // create a jquery object
      .val() // call the val method on it
  )

However, the value could be cached: var val = $(this).val();. Then the line might be less confusing to you: /yourregex/.test(val)

answered May 18, 2012 at 16:02

ThiefMaster

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1 Comment

ThiefMaster Over a year ago

It matches a string that is empty or consists of nothing but whitespace.

user1115652 · Accepted Answer · 2012-05-18 16:02:26Z

2

/^\s*$/ is a regular expression literal and it has a test method which is being called. The brackets are from the if condition which is bigger.

Since javascript is fully object oriented even literals can have methods.

answered May 18, 2012 at 16:02

user1115652

1 Comment

Chris22 Over a year ago

+1. if I could select more than one answer, I would. Thanks for explaining that regular expressions are literals and have methods. That really helped.

Ash Burlaczenko · Accepted Answer · 2012-05-18 16:04:03Z

2

The code is fine. If you think its unreadable why not create the regex first

var regex = /^\s*$/;
if(regex.test($(this).val())
    ...

answered May 18, 2012 at 16:04

Ash Burlaczenko

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3 Comments

ThiefMaster Over a year ago

I'm pretty sure you pass a string when using new RegExp(). However, don't do this unless you have to. Using a string means you have to double-escape backslashes etc.

Ash Burlaczenko Over a year ago

Oh right. It's a while since I've done regexs in JS. Thanks for the input

Chris22 Over a year ago

@Ash, yes if it were coded like that, I would have understood it a ilttle better. I didn't know reg expressions could have methods

Sampson · Accepted Answer · 2012-05-18 19:01:24Z

2

/^\s*$/.test( $(this).val() )

The first part is a regular expression - not a string or anything else. As such, it begins and ends with deliminters / and /.

Using .match is sometimes more legible as it doesn't appear to have some strange unbound item floating around in the source:

$(this).val().match(/^\s*$/);

This particular expression, broken down, reads like this:

/^   // Beginning of String
\s*  // Space, zero or more times
$/   // End of String

So it will test positive if there are zero or more spaces, from start to finish, and nothing else.

edited May 18, 2012 at 19:01

answered May 18, 2012 at 16:03

Sampson

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3 Comments

ThiefMaster Over a year ago

There actually shouldn't be a paren at the beginning - he copied from his if() statement

Chris22 Over a year ago

@JonathanSampson, +1 this helps me as well to understand. I found this link on google developer.mozilla.org/en/JavaScript/Guide/Regular_Expressions

Sampson Over a year ago

@Chris22 The Mozilla Developer network is always helpful. I also noted that you had asked what this expression meant, so I've updated my answer to contain that explanation as well.

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