Explain javascript code with regular expressions

Question

I navigated to a file while browsing the source code of a project. It is a javascript file and it contains the following:

var Tools = {};
... 
Tools.EMAIL_ADDR_PATTERN = /\w+@[a-zA-Z0-9_-]+?(?:\.[a-zA-Z]{2,6})+/gim;

What type is the EMAIL_ADDR_PATTERN? Why is capitalised? How can be invoked?

This might be quite simple, however my js knowledge is very limited.

why don't you just google regular expressions? MDN and a small toy. — mechalynx
– mechalynx, Commented Jul 14, 2014 at 13:01
[Any alpha numeric char with no length limit]@[Any alpha numeric char, _ and - with no length limit].[Any char to a to z, A to Z with limited length between 2 and 6] in short. Reference — DontVoteMeDown
– DontVoteMeDown, Commented Jul 14, 2014 at 13:02
should be noted that the a-z A-Z is redundant, as it's matched case-insensitive (/..../i) anyway. — amenthes
– amenthes, Commented Jul 14, 2014 at 13:06
@amenthes quite ironic that the author used \w in the beginning but then went for [a-zA-Z0-9_-] instead of [\w-]. — HamZa
– HamZa, Commented Jul 14, 2014 at 13:08

deceze · Accepted Answer · 2014-07-14 13:02:01Z

3

This is literally what it looks like. A regular expression literal is assigned to the variable Tools.EMAIL_ADDR_PATTERN. There's nothing special about capitalisation, it's likely a convention in the code to emulate constants.

answered Jul 14, 2014 at 13:02

deceze♦

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erosman · Accepted Answer · 2014-07-14 13:06:01Z

1

What type is the EMAIL_ADDR_PATTERN? Why is capitalised?

EMAIL_ADDR_PATTERN is the name of the property that the programmer has chosen. It can be anything.

How can be invoked?

Use the pattern in any method that accepts Regular Expression pattern such as:string.match(Tools.EMAIL_ADDR_PATTERN)

answered Jul 14, 2014 at 13:06

erosman

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Hugo Wood · Accepted Answer · 2014-07-14 13:07:47Z

1

Short answer: it's regular expression literal.

You can open a console in your favorite browser (press F12) and try for yourself:

> var r = /\w+@[a-zA-Z0-9_-]+?(?:\.[a-zA-Z]{2,6})+/gim
> typeof(r)
"object"
> r.constructor
function RegExp() { [native code] }
> r.test("hello world")
false
> r.test("[email protected]")
true

A REPL console is always a good friend. The Chrome one will even auto-complete method names so you can discover them more easily.

answered Jul 14, 2014 at 13:07

Hugo Wood

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Peter Aron Zentai · Accepted Answer · 2014-07-14 13:03:51Z

0

This is how you would use it:

var email = "[email protected]";

if (email.match(Tools.EMAIL_ADDR_PATTERN)) {
  alert("this is an email");
}

answered Jul 14, 2014 at 13:03

Peter Aron Zentai

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Comments

Raven · Accepted Answer · 2014-07-14 13:16:08Z

0

Tools.EMAIL_ADDR_PATTERN just to validate the email string.

you can use like:

var flag = /\w+@[a-zA-Z0-9_-]+?(?:\.[a-zA-Z]{2,6})+/gim.test('[email protected]')

flag will be (boolean)true

answered Jul 14, 2014 at 13:16

Raven

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