Utf8String

While this string implementation has all the necessary bits to sometime grow into a full-fledged implementation, this is unlikely to happen firstly because of time needed, but also because such an implementation require a custom regular expression engine.

Simple Example

const str = new Utf8String('aaaabc');
const searchStr = new Utf8String('aab');
const result = str.substring(str.find(searchStr));
console.log(String(result)); // "aabc"

For more examples please refer to the tests.

Immutability

All string operation return a new Utf8String object.

Iterating a string

Because of the nature of UTF-8 encoding (and Unicode in general), a JavaScript's String style random access to a string is not very desirable for performance reasons since you have to always iterate from the start of the string and count the code points.

Moreover code points may not be what you want to count, as, for example grapheme clusters should be used for counting what would one visually consider "characters".

This is why Utf8String exposes a codePoints() method that returns an iterator over unicode code points, which is also aliased to an [Symbol.iterator]() method so that it is easy to use Utf8String in for .. of constructs and with other functions and constructs that expect an object conforming to an iterator protocol such as Array.from() or spread operator.

Utf8String also provides a bytes() iterator that could be used for low-level access to the string.

Size of a string

The same as with iteration, depending on your particular requirements you might have a different definition of a size (or a length) of a string. This is why instead of providing a multitude of instance methods Utf8String library takes a different approach with delivering a single class utility method called Utf8String.count(), which accepts and iterable, such as one returned by codePoints() or bytes() instance method.

This approach also allows to provide additional iterators such as characters (grapheme clusters), or even words as separate packages while making use of default length / counting facilities.