How to Capitalize First Letter in JavaScript

JavaScript is a popular front end language that allows web developers and programmers to easily build websites. Often web developers may need to make the first letter upper case in a string or sentence. In this article, we will learn how to capitalize first letter in JavaScript.

How to Capitalize First Letter in JavaScript

Here are the steps to capitalize first letter in JavaScript. Let us say you have the following string in JavaScript.

str = "jim"

We will use toUpperCase() function to convert the first character to upper case. This function converts all characters in a string to upper case, so we will call this function only on the first character. We will use charAt(0) function to get the first character that is the character at position 0.

str.charAt(0).toUpperCase() //J

To the above result, we will append rest of the unmodified string. For this purpose, we will use slice() function. slice() function allows you to extract a substring from a given string by mentioning the starting character, and optionally specifying the last character

str.slice(1) //im

We will concatenate the two above results to get our desired string.

str.charAt(0).toUpperCase() + str.slice(1);

Putting together everything, we will create a simple function to help us convert any input string’s first character as capital letter.

function capitalizeFirstLetter(string) {
  return string.charAt(0).toUpperCase() + string.slice(1);
}

Here is how to call the function.

console.log(capitalizeFirstLetter('jim')); // Jim

If you want, you can also add this function to String prototype so that it is easy to call.

String.prototype.capitalize = function() {
  return this.charAt(0).toUpperCase() + this.slice(1);
}

Once you have defined the prototype function, you can easily call it directly from any string as shown below.

str = 'jim';
console.log(str.capitalize()); //Jim

In this article, we have learnt how to capitalize the first letter of string in JavaScript. You can include it as a part of a bigger module or run it as a standalone function.

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