JavaScript - Chapter 9 - TypeConversion and Regular Expressions

www.webstackacademy.com Type Conversion & Regular Expressions JavaScript

www.webstackacademy.com  Type Conversion  Regular Expression Table of Content

www.webstackacademy.com ‹#›www.webstackacademy.com Type Conversion (JavaScript)

www.webstackacademy.com Type Conversion JavaScript variables can be converted to a new variable and another data type:  By the use of a JavaScript function  Automatically by JavaScript itself

www.webstackacademy.com Converting Number to String  The String() and toString() can convert number to strings String(234); //234 var n=45; var x=n.toString(); // Result x is 45

www.webstackacademy.com Converting Booleans to String The String() and toString() can convert boolean to string. String(false); // return false false.toString(); // return false

www.webstackacademy.com Converting Date to String The String() and toString() can convert date to string. String(Date()); // or Date().toString();

www.webstackacademy.com Converting String to Numbers Option Description Number() Convert Strings to numbers parseFloat() Parses a string and returns a floating point number parseInt() Parses a string and returns an Integer

www.webstackacademy.com Unary +Operator The unary + operator can be used to convert a variable to a number. <body> <button onclick="checkType()">Click this button</button> <p id="ex"></p> <script> function checkType() { var y = "5"; var x = + y; document.getElementById("ex").innerHTML = typeof y + "<br>" + typeof x; } </script>

www.webstackacademy.com Automatic Type Conversion <script> document.write((3 + null )+ "<br>"); //returns 3 document.write(("3" + null) + "<br>");//returns 3null document.write("3" + 2 + "<br>");//returns 32 document.write(("3" - 2) + "<br>"); //returns 1 document.write(("5" * "2") + "<br>"); // returns 10 </script>

www.webstackacademy.com Exercise  Revisit the rectangle program (area & perimeter). Check the output with and without converting the input values.  Write a JavaScript program to convert current date into string.

www.webstackacademy.com ‹#›www.webstackacademy.com Regular Expression (RegEx) (JavaScript)

www.webstackacademy.com Regular Expression  Regular expressions are used for defining String patterns that can be used for searching, manipulating and editing a text.  A regular expression, regex or regexp, in theoretical computer science.  The process of searching text to identify matches—strings that match a regex's pattern—is pattern matching.  In JavaScript, regular expressions are also objects.  Regular expressions can be used to perform text search and text replace operations.

www.webstackacademy.com Regular Expression  Pattern:  Pattern specifications consist of a series of characters  These characters have a special meaning  They are also known as meta characters Syntax: var match = new RegExp(pattern, modifiers) (or) var match = /pattern/modifiers

www.webstackacademy.com Regular Expression  Modifiers are a series of characters indicating various options  They are optional in a regular expression  This syntax is borrowed from Perl, supports some of them  Perl was originally designed for pattern matching Option Description g Global matching. When using the replace() method, specify this modifier to replace all matches, rather than only the first one. i Case insensitive matching m Multi-line mode. In this mode, the caret and dollar match before and after newlines in the subject string

www.webstackacademy.com Regular Expression var pattern = /Fruit/i; Option Description /Fruit/i Regular Expression Fruit Search pattern i The search should be case insensitive

www.webstackacademy.com Regular Expression patterns Character Meaning Indicates that the next character is special and not to be interpreted literally ^ Matches the beginning of the string or line. $ Matches the end of the string or line. * Matches the previous character 0 or more times. + Matches the previous character 1 or more times. n Matches a New line ? Matches the previous character 0 or 1 time. . Find a single character, except newline or line terminator

www.webstackacademy.com Regular Expression Pattern Brackets are used to find range of characters. Expression Description [abc] Find any of the characters between the bracket [^abc] Find any character NOT between the brackets [0-9] Find any of the digits between the brackets [^0-9] Find any character NOT between the brackets (any non-digit) (x|y) Find any of the alternatives separated with |

www.webstackacademy.com Regular Expression Example <script> function upper_case(str) { var regexp = /^[A-Z]/; if (regexp.test(str)) { console.log("String's first character is uppercase"); } else { console.log("String's first character is not uppercase"); } } upper_case('Webstack Academy'); upper_case('webstack academy'); </script>

www.webstackacademy.com Metacharacters Meta character Description d Find a digit D Find a non digit character w Find a word character W Find a non word character s Find a whitespace character S Find a non-whitespace character b Find a match at the beginning or end of the word B Find a match not at the beginning or end of the word 0 Find a Null character uxxxx Find a uni-code character specified by the hexadecimal number xxxx

www.webstackacademy.com Examples var pattern =/^abc/; var pattern = /xy{3,5}z/; var pattern =/[a-z]/; var pattern = /abc.d/; Matches only those string beginning with abc. Matches a single “x” followed by y characters between three and five and then the letter z Matches any lowercase alphabetic character Matches any character except a newline

www.webstackacademy.com Exercise  WAP that will match any string containing “world”.  WAP to check whether the given string is alphanumeric or not  WAP to validate the mobile number in a given format (+91 98412 32534)  WAP to validate credit card in a given format (4312-8763-9823-1234)  WAP to validate a discount code (PIZDIS400)  Invalid format  Invalid coupon code

www.webstackacademy.com ‹#›www.webstackacademy.com Regular Expression Methods (JavaScript)

www.webstackacademy.com The Exec() Method The exec() method of the RegExp object is used to execute the search for a match in a specified string. Example: /c/.exec("In JavaScript, regular expressions are also objects."); Syntax: Regexp.exec(str);

www.webstackacademy.com The test() Method  The test() method of the RegExp executes a search for a match between a regular expression and a specified string.  It will return true or false. Syntax: Regexp.test(str);

www.webstackacademy.com Example <script> regExpr = new RegExp('like','g') // Define a string. str1 = 'Happiness radiates like the fragrance from a flower'; // Check whether regular expression exists in the string. if (regExpr.test(str1)) { document.write("'like' is found in " + str1); } </script>

www.webstackacademy.com ‹#›www.webstackacademy.com String Methods for Regular Expression (JavaScript)

www.webstackacademy.com String Methods for Regular Expressions It will return the index of character at which the first matching substrings begins. <script> var str = "I like apple"; var n = str.search(/Apple/i); document.write(n); </script> Output : 7 Syntax: str.search(pattern);

www.webstackacademy.com The split() • The split() method splits a string into sub strings and return them in an array • Separator is used to split the string • Limit specifies the number of splits Syntax: str.split(separator,limit); <script> var str = “10/3/5/6/5"; var split = str.split(/[/]+/); document.write(split); </script>

www.webstackacademy.com The replace() var str = "Hello.How are You?"; // Replace first dot with exclamation mark (!) var res = str.replace(/./, "!"); alert(res); Syntax: str.search(searchvalue,newvalue); • The search() method searches for the given String / RegExp, replaces new value • In case of RegExp the first match is replaced. For all replacements use ‘g’ modifier

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JavaScript - Chapter 9 - TypeConversion and Regular Expressions

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