Javascript - RegExp
A regular expression is an object that describes a pattern of characters.
When you search in a text, you can use a pattern to describe what you are searching for.
A simple pattern can be one single character.
A more complicated pattern can consist of more characters, and can be used for parsing, format checking, substitution and more.
Regular expressions are used to perform powerful pattern-matching and "search-and-replace" functions on text.
JavaScript RegExp Syntax
var patt=new RegExp(pattern,modifiers);
or more simply:
var patt=/pattern/modifiers;
- pattern specifies the pattern of an expression
- modifiers specify if a search should be global, case-sensitive, etc.
Modifiers are used to perform case-insensitive and global searches.
The i modifier is used to perform case-insensitive matching.
The g modifier is used to perform a global match (find all matches rather than stopping after the first match).
JavaScript RegExp Modifiers Example 1
Do a case-insensitive search for "Leakbali" in a string:
var str="Visit Leakbali";
var patt1=/Leakbali/i;
The
marked text below shows where the expression gets a match:
Visit Leakbali
JavaScript RegExp Modifiers Example 2
Do a global search for "is":
var str="Is this all there is?";
var patt1=/is/g;
The
marked text below shows where the expression gets a match:
Is this all there is?
JavaScript RegExp Modifiers Example 3
Do a global, case-insensitive search for "is":
var str="Is this all there is?";
var patt1=/is/gi;
The marked text below shows where the expression gets a match:
Is this all there is?
The test() method searches a string for a specified value, and returns true or false, depending on the result.
The following example searches a string for the character "e":
JavaScript test() Example
var patt1=new RegExp("e");
document.write(patt1.test("The best things in life are free"));
Since there is an "e" in the string, the output of the code above will be:
true
The exec() method searches a string for a specified value, and returns the text of the found value. If no match is found, it returns null.
The following example searches a string for the character "e":
JavaScript exec() Example 1
var patt1=new RegExp("e");
document.write(patt1.exec("The best things in life are free"));
Since there is an "e" in the string, the output of the code above will be:
e
