JavaScript Program to Capitalize the First Letter of Every Sentence in a String

In this article, we will see how Capitalizing the first letter of every sentence in a string is a common text manipulation task in JavaScript. It involves identifying sentence boundaries and ensuring that the first letter of each sentence is in uppercase.

Examples:

Input: "this is Geeks for Geeks website. hello there!"
Output: "This is Geeks for Geeks website. Hello there!"
Input: "hello. how are you."
Output: "Hello. How are you."

Method 1: Using Regular Expressions:

• Split the text into sentences using a regular expression.
• Capitalize the first letter of each sentence using a combination of toUpperCase() and substring().

Example: Here, is the implementation of the above approach

Javascript

function capitalizeSentences(text) {

    // Split the text into sentences
    // using regular expressions
    const sentences = text.split(/\.|\?|!/);

    // Capitalize the first letter of each sentence
    const capitalizedSentences = sentences
        // Remove empty sentences
        .filter(sentence =>
            sentence.trim() !== '')
        .map(sentence =>
            sentence.trim()[0]
                .toUpperCase() +
            sentence.trim().slice(1));

    // Join the sentences back together
    return capitalizedSentences.join('. ') + '.';
}

const inputText =
    `geeks for geeks for
     students.hello students.`;
const result = capitalizeSentences(inputText);
console.log(result);

Output

Geeks for geeks for 
     students. Hello students.

Method 2: Using slice() Method

• Split the text into an array of sentences using the split() method with sentence-ending punctuation marks as delimiters.
• Capitalize the first letter of each sentence and join the sentences back together.

Example: Here, is the implementation of the above approach

Javascript

function capitalizeSentences(text) {
    const sentences =
        text.split(/[.!?]/)
            .filter(sentence =>
                sentence.trim() !== '');
    for (let i = 0; i < sentences.length; i++) {
        sentences[i] =
            sentences[i].trim()[0].toUpperCase() +
            sentences[i].trim().slice(1);
    }
    return sentences.join('. ') + '.';
}
const inputText = "geeks for geeks. hello students."
const result = capitalizeSentences(inputText);
console.log(result);

Output

Geeks for geeks. Hello students.