You have to use charAt(), toUpperCase() and slice() method to capitalize first letter in JavaScript. The charAt() function returns the character at a given position in a string.
str.charAt(0).toUpperCase() + str.slice(1);
And toUpperCase() function converts all the characters of an input string to uppercase, where slices a given string from a specified “start” position until the specified “end” position.
JavaScript capitalize first letter
Simple example code.
<!DOCTYPE html>
<html>
<body>
<script>
const str = 'abc efg';
const res = str.charAt(0).toUpperCase() + str.slice(1);
console.log(res);
</script>
</body>
</html>
Output:

How do I make the first letter of a string uppercase in JavaScript?
Answer: "this is a test"
→ "This is a test"
The basic solution is:
function capitalizeFirstLetter(string) {
return string.charAt(0).toUpperCase() + string.slice(1);
}
console.log(capitalizeFirstLetter('foo')); // Foo
Do comment if you have any doubts or suggestions on this JS basic topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version

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