Locating Substrings

To find the position of a specific character or sequence within a string, use indexOf(). This method returns the index of the first occurrence or -1 if the value is not found.

const message = "Learn, build, and share";

// Finding the first occurrence of 'b'
const firstB = message.indexOf("b"); // returns 7

// Starting search from index 10
const nextA = message.indexOf("a", 10); // returns 18

Accessing Individual Chraacters

The charAt() method retrieves the character at a specific index. Modern JavaScript also supports bracket notation for the same purpose.

const label = "Frontend";
console.log(label.charAt(4)); // "t"
console.log(label[0]);        // "F"

Extracting Portions of a String

JavaScript provides several ways to extract parts of a string: slice(), substring(), and substr().

• slice(start, end): Extracts from start up to, but not including, end.
• substring(start, end): Operates similarly to slice but handles negative indices different (treating them as 0).
• substr(start, length): Extracst a specific number of characters starting from a specified index.

const sequence = "Modern Web Development";

console.log(sequence.slice(0, 6));      // "Modern"
console.log(sequence.substring(7, 10)); // "Web"
console.log(sequence.substr(11, 11));   // "Development"

Splitting and Replacing

The split() method converts a string into an array based on a delimiter. The replace() method searches for a pattern and substitutes it with a new string.

const csv = "red,green,blue";

// Convert string to array
const colors = csv.split(","); // ["red", "green", "blue"]

// Replace content (case-sensitive by default)
const updatedCsv = csv.replace("red", "yellow"); // "yellow,green,blue"

Common String Method Reference