Completely confused! -- Regular Expressions

From my research we should use Regular Expressions in 2 ways:

1) Using literal syntax.
2) When you need to dynamically construct the regular expression, via the RegExp() constructor.

The literal syntax looks something like: var RegularExpression = /pattern/
while the RegExp() constructor method looks like var RegularExpression = new RegExp("pattern");

Well my code NEVER works when I use double quotes. It ONLY works the way I present below:

var RegExp1 = new RegExp(/^.*$/);
if (!RegExp1.test(globalValueControl.value))
{
//bla bla }

Also, I got the sample code below and it's using a SINGLE quote:

var octet = '(?:25[0-5]|2[0-4][0-9]|1[0-9]{2}|[1-9][0-9]|[0-9])';
var ip = '(?:' + octet + '\\.){3}' + octet;
var RegExp1 = new RegExp('^' + ip + '$' );

Not sure how and why that works. My code did not work with double or single quotes, what am I missing here? What is the right process/standard here?

Thank you

 

you can create regex object by both

var re = new RegExp('.*');
var re =/.*/;

the later is better since you must double backslash the first one
then its just to feed it with a string to execute

var result = re.exec('Your text');

 

yes, I understand what you typed but as I mentioned in my first statement, it won't work for me.
The only way it works is if I use the the RegExp() constructor passing the pattern between "/" which is so weird:

var RegExp1 = new RegExp(/^.*$/);
if (!RegExp1.test(globalValueControl.value))

 

That is because sometimes you need quote the special charectors in your regexp string. Coz I don't know what is exactly your regexp doing for. I suggest a way of debug this kind of problem.

Add an <textarea id="tmp"> tag in your page. write the regexp string into the textarea. See if it's still your original regexp.