Methods cannot be called on TypeScript primitive strings

In my exploration of TypeScript, I came across the concept that the string primitive type does not have any methods and is simply a value. To utilize methods such as toLowerCase(), one must work with the String type instead.

Curious about this distinction, I decided to experiment:

let s = "Hello";
console.log(typeof(s));   // string
s = s.toLowerCase();

Surprisingly, I found that I could successfully call the toLowerCase method on my string variable. This has left me puzzled – why was this possible?

Furthermore, I am interested in understanding the added value of using String over the string primitive type.

Any insights you can provide would be greatly appreciated.

Answer №1

because it's defined as a type

If you're unsure, take a look at the TypeScript source code. It's open source and freely accessible for anyone to learn from.

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