String Manipulation
String Comparison
String comparison in JavaScript is done using various methods such as localeCompare(), and simply comparing the strings using operators like ===. Here's a brief explanation of each:
localeCompare()
localeCompare()This method compares two strings in the current locale. It returns a number indicating whether the reference string comes before, after, or is equivalent to the compared string.
const str1 = "apple";
const str2 = "banana";
console.log(str1.localeCompare(str2)); // Output: -1 (str1 comes before str2)Operator Comparison
Strings can also be compared using operators like ===, which compares both value and type.
Unicode
Unicode is a character encoding standard that assigns a unique numeric value to each character, > including letters, digits, and symbols, across different writing systems and languages. > JavaScript uses Unicode to represent and process string data.
Here are some key points about Unicode in JavaScript:
Characters in JavaScript strings are represented using their Unicode code points.
Unicode allows for encoding characters beyond the ASCII range, enabling support for a wide range of languages and symbols
JavaScript methods includes
charCodeAt()andString.fromCharCode()for working with Unicode code points.
Regular Expressions
Regular expressions, often abbreviated as "regex" are powerful tools for pattern matching and string manipulation in JavaScript. It allows you to search for, extract, and also can be used to replace patterns within strings.
common use cases for regular expressions:
Validating input: Regex can be used to ensure that user input matches a specific pattern, such as an email address or phone number.
// Regular expression pattern for validating email addresses
const emailPattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
// Function to validate email input
function validateEmail(email) {
return emailPattern.test(email);
}
// Example usage
const userEmail = "example@email.com";
if (validateEmail(userEmail)) {
console.log("Email is valid!");
} else {
console.log("Invalid email!");
}a regular expression pattern emailPattern which checks for a string that starts (^) and ends ($) with a sequence of characters that do not include whitespace ([^\s@]+), followed by an "@" symbol, then another sequence of characters that do not include whitespace, then a dot ".", and finally another sequence of characters that do not include whitespace.
Search and replace: Regex allows you to find all occurrences of a pattern within a string and replace them with another string.
// Sample string
let text =
"The quick brown fox jumps over the lazy dog. The quick fox is faster than the lazy dog.";
// Regular expression pattern to search for occurrences of "fox" and replace with "cat"
const regex = /fox/g; // "g" flag indicates global search (find all occurrences)
// Replacement string
const replacement = "cat";
// Perform the search and replace using the replace() method
const newText = text.replaceAll(regex, replacement);
// Output the result
console.log(newText);Data extraction: Regex can extract specific parts of a string, such as extracting numbers or extracting text between delimiters.
// Sample string containing numbers
const text =
"The price of the product is $25.50 and the shipping cost is $5.75.";
// Regular expression pattern to extract numbers (including decimal numbers)
const numberPattern = /\d+(\.\d+)?/g;
// Extracting numbers from the text using the match() method
const numbers = text.match(numberPattern);
// Output the extracted numbers
console.log(numbers);To learn & practice RegEx
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