CODEWITHSUNDEEP
javascriptstringunicode-stringcodepoint
ppt
ppt

Reputation: 1326

How do I reverse `String.fromCodePoint`, i.e. convert a string to an array of code points?

String.fromCodePoint(...[127482, 127480]) gives me a flag of the US (🇺🇸).

How do I turn the flag back to [127482, 127480]?

Upvotes: 2

Views: 1330

Answers (1)

T.J. Crowder
T.J. Crowder

Reputation: 1074028

You're looking for codePointAt, perhaps using spread (etc.) to convert back to array and then mapping each of them.

console.log(theString.codePointAt(0)); // 127482
console.log(theString.codePointAt(2)); // 127480
// Note −−−−−−−−−−−−−−−−−−−−−−−−−−^
// It's 2 because the first code point in the string occupies two code *units*

or

const array = [...theString].map(s => s.codePointAt(0));
console.log(array); // [127482, 127480]

or skipping an interim step as Sebastian Simon pointed out via Array.from and its mapping callback:

const array = Array.from(theString, s => s.codePointAt(0));
console.log(array); // [127482, 127480]

Example:

const theString = String.fromCodePoint(...[127482, 127480]);

console.log(theString.codePointAt(0)); // 127482
console.log(theString.codePointAt(2)); // 127480

const array = [...theString].map(s => s.codePointAt(0));
console.log(array);  // [127482, 127480]

const array2 = Array.from(theString, s => s.codePointAt(0));
console.log(array2); // [127482, 127480]

Spread and Array.from both work by using the strings iterator, which works by code points, not code units like most string methods do.

Upvotes: 5

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