What is RegExp Modifiers in JavaScript?

[Flaco]

I have done some basic programs in JavaScript. But I am confused when I have to use the RegExp in coding. Can someone explain me what is the RegExp and why it is used for.?? I have used it twice but I don't know the exact purpose of that.! Also later I came to know about the RegExp Modifiers. So please explain me, what is the RegExp Modifiers in JavaScript? It will be more appreciable if somebody can give me some coding regarding the same.!!

[Allan.d]

The RegExp stands for the regular expression. A regular expression is written in the form of modifiers or the pattern. Here the modifiers are a series of characters indicating various options, while the pattern is the regular expression itself. While the the modifiers part is an optional. The following modifiers are supported by the JavaScript :

1. /i makes the regexp match case insensitive.
2. /g enables global matching.
3. /m enables multi-line mode.

If you want to combine multiple modifiers by stringing them together, you can do that by using the /regex/gim.

[Warner]

I think that you should know about the regular expression, before you start the RegExp Modifiers. A regular expression is an object that describes a pattern of characters. You can use a pattern to describe what you are searching for when you search in a text. A simple pattern can be one single character whereas more complicated pattern can consist of more characters and that are used for doing the parsing, format checking, substitution, etc. For doing the powerful pattern-matching and search-and-replace functions on text, regular expressions are used. Below is the syntax for the same :

var txt=new RegExp(pattern,modifiers);

or more simply:

var txt=/pattern/modifiers;

In above example, modifiers specify if a search should be global, case-sensitive, etc. and the pattern specifies the pattern of an expression.

[Viensterrr]

The RegExp Modifiers are used to perform case-insensitive and global searches. In which there are i and g modifier. If you want to perform case-insensitive matching, then you will have to use i modifier. And if you want to perform a global match then you will have to use the g modifier. In the following example, I have tried to explain you how to use the i modifier for case-insensitive.
Do a case-insensitive search for "lessons" in a string :

var str="Learn Lessons";
var patt1=/lessons/i;

The underlined text below shows where the expression gets a match :

Learn Lessons

[Solitario]

Give can glance at the following example to know how to use the g modifier.
Do a global search for "as":

var str="Assure me as soon as possible";
var patt1=/is/g;

The output of the above RegExp Modifiers will be :

Assure me as soon as possible

The underlined text shows where the expression gets a match.

If you do the global, case-insensitive search for the above same example,

var str="Assure me as soon as possible";
var patt1=/is/gi;

The output will be like this :

Assure me as soon as possible