Javascript-16-Regex

Regular Expression

Syntax: /pattern/modifiers;

pattern - the string pattern that needs to be searched

modifiers - the condition if any during the search for the pattern.

Regular Expression Modifiers:

i - Perform case-insensitive matching

g - Perform a global match (find all matches rather than stopping after the first match)

m - Perform multiline matching

Regular Expression Patterns:

[abc] - Find any of the characters between the brackets

[0-9] - Find digits in the range in the brackets

[x|y] - Find x or y giving in the bracket

Metacharacters:

Quantifiers:

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Regular expressions can be used with 2 of String methods:

1)str.search(""); //returns index of first occurence

Example:

• var str = "Visit W3Schools"; 
• var n = str.search(/w3schools/i); // returns 6

2)str.replace(""); //returns string by replacing string occurence

Example:

• var str = "Visit Microsoft!";
• var res = str.replace(/microsoft/i, "W3Schools"); //returns Visit W3Schools! for "res" value

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Regex Object and its methods:

test(): It searches a string for a pattern, and returns true or false, depending on the result.

• var patt = /e/;
  patt.test("The best things in life are free!"); 
• (or) 
• /e/.test("The best things in life are free!");
• Results in "true"

exec(): It searches a string for a specified pattern, and returns the found text. If text not found, returns null;

• /e/.exec("The best things in life are free!");
• Results in "e"

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