What is the JavaScript code to uppercase the first letter of a string?

Here's the JavaScript code to uppercase the first letter of a string:

There are several ways to achieve this, but a common and concise method is using JavaScript's built-in string methods. This method involves extracting the first character of the string, converting it to uppercase, and then concatenating it with the rest of the string.

Here's the code:

function uppercaseFirstLetter(str) {
  if (!str) {
    return str; // Return empty string if input is empty or null
  }
  return str.charAt(0).toUpperCase() + str.slice(1);
}

// Example usage:
let myString = "hello world";
let uppercasedString = uppercaseFirstLetter(myString);
console.log(uppercasedString); // Output: Hello world

Explanation:

1. function uppercaseFirstLetter(str): This defines a function named uppercaseFirstLetter that takes a string str as input.

2. if (!str) { return str; }: This is an important check to handle cases where the input string is empty or null. If the string is empty, the function immediately returns it to avoid errors.

3. str.charAt(0).toUpperCase(): This part of the code extracts the first character of the string using charAt(0) and then converts it to uppercase using toUpperCase().

4. str.slice(1): This part extracts the rest of the string starting from the second character (index 1) using slice(1). The slice() method returns a new string containing the portion of the string beginning at the specified index.

5. return str.charAt(0).toUpperCase() + str.slice(1);: Finally, the function concatenates the uppercased first character with the rest of the string and returns the new string.

Alternative Method using Substring:

You could also use substring instead of slice:

function uppercaseFirstLetter(str) {
  if (!str) {
    return str;
  }
  return str.substring(0, 1).toUpperCase() + str.substring(1);
}

The substring method works similarly to slice, extracting a portion of the string. In this context, both substring and slice will achieve the same result.

Using this function, you can easily uppercase the first letter of any string in your JavaScript code. Remember to handle edge cases like empty or null strings to make your code more robust. Is there anything else I can help you with?

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