How do I make the first letter of a string uppercase in JavaScript?

Question

How do I make the first letter of a string uppercase, but not change the case of any of the other letters?

For example:

• \"this is a test\"

Answer 1

CSS only

p::first-letter {
  text-transform: uppercase;
}

• Despite being called ::first-letter, it applies to the first character, i.e. in case of string %a, this selector would apply to % and as such a would not be capitalized.
• In IE9+ or IE5.5+ it's supported in legacy notation with only one colon (:first-letter).

ES2015 one-liner

Since there are numerous answers, but none in ES2015 that would solve original problem efficiently, I came up with the following:

const capitalizeFirstChar = str => str.charAt(0).toUpperCase() + str.substring(1);

Remarks

• parameters => function is so called arrow function.
• I went with name capitalizeFirstChar instead of capitalizeFirstLetter, because OP didn't asked for code that capitalizes the first letter in the entire string, but the very first char (if it's letter, of course).
• const gives us the ability to declare capitalizeFirstChar as constant, which is desired since as a programmer you should always explicitly state your intentions.
• In the benchmark I performed there was no significant difference between string.charAt(0) and string[0]. Note however, that string[0] would be undefined for empty string, so it should be rewritten to string && string[0], which is way too verbose, compared to the alternative.
• string.substring(1) is faster than string.slice(1).

Benchmark

• 4,956,962 ops/s ±3.03% for this solution,
• 4,577,946 ops/s ±1.2% for the most voted answer.
• Created with JSBench.me on Google Chrome 57.