Advanced JavaScript String Methods

JavaScript provides a rich set of methods for manipulating strings. In this guide, we’ll explore some of the more advanced string methods that can help you become a more efficient JavaScript developer.

1. string.repeat()

The repeat() method constructs and returns a new string containing a specified number of copies of the original string.

const mood = "Happy! ";

console.log(`I feel ${mood.repeat(3)}`);
// Output: "I feel Happy! Happy! Happy! "

2. string.replace() and string.replaceAll()

The replace() method returns a new string with the first occurrence of a pattern replaced by a specified replacement. The replaceAll() method, on the other hand, replaces all occurrences.

const paragraph = "I think Ruth's dog is cuter than your dog! Ruth's";

console.log(paragraph.replace("Ruth's", "my"));
// Output: "I think my dog is cuter than your dog! Ruth's"

console.log(paragraph.replaceAll("Ruth's", "my"));
// Output: "I think my dog is cuter than your dog! my"

// Using regex
const regex = /Dog/gi;
console.log(paragraph.replaceAll(regex, "ferret"));
// Output: "I think Ruth's ferret is cuter than your ferret! Ruth's"

3. string.slice()

The slice() method extracts a section of a string and returns it as a new string, without modifying the original string.

const str1 = "The morning is upon us.";
console.log(str1.slice(1, 8)); // "he morn"
console.log(str1.slice(4, -2)); // "morning is upon u"
console.log(str1.slice(12)); // "is upon us."
console.log(str1.slice(-5, -2)); // "n u"

4. string.split()

The split() method divides a string into an ordered list of substrings, puts these substrings into an array, and returns the array.

const str = "The quick brown fox jumps over the lazy dog.";

const words = str.split(" ");
console.log(words[3]); // "fox"

const chars = str.split("");
console.log(chars[8]); // "k"

const strCopy = str.split();
console.log(strCopy); // Array ["The quick brown fox jumps over the lazy dog."]

const wordsLimit = str.split(" ", 5);
console.log(wordsLimit); // ["The", "quick", "brown", "fox", "jumps"]

5. string.substring()

The substring() method returns the part of the string between the start and end indexes, or to the end of the string.

const str = "Mozilla";

console.log(str.substring(1, 3)); // "oz"
console.log(str.substring(2)); // "zilla"
console.log(str.substring(str.length - 4)); // "illa"

6. string.toLowerCase() and string.toUpperCase()

These methods convert a string to lowercase or uppercase respectively.

const name = "Manoj";
console.log(name.toLowerCase()); // "manoj"
console.log(name.toUpperCase()); // "MANOJ"

7. string.trim(), trimStart(), and trimEnd()

The trim() method removes whitespace from both ends of a string. trimStart() and trimEnd() remove whitespace from the beginning or end of a string, respectively.

const greeting = "   Hello world!   ";

console.log(greeting.trim()); // "Hello world!"
console.log(greeting.trimStart()); // "Hello world!   "
console.log(greeting.trimEnd()); // "   Hello world!"

8. string.valueOf() and string.toString()

Both valueOf() and toString() return the primitive value of a String object.

const stringObj = new String("foo");

console.log(stringObj); // String { "foo" }
console.log(stringObj.valueOf()); // "foo"
console.log(stringObj.toString()); // "foo"

console.log(typeof stringObj); // "object"
console.log(typeof stringObj.toString()); // "string"

Conclusion

These advanced string methods provide powerful tools for manipulating and working with strings in JavaScript. By mastering these methods, you can write more efficient and cleaner code when dealing with string operations.

Remember to always consider the immutability of strings in JavaScript - these methods return new strings rather than modifying the original.

Happy coding!