The [@@iterator]() method of String values implements the iterable protocol and allows strings to be consumed by most syntaxes expecting iterables, such as the spread syntax and for...of loops. It returns a string iterator object that yields the Unicode code points of the string value as individual strings.
Syntax
string[Symbol.iterator]()
Parameters
None.
Return value
A new iterable iterator object that yields the Unicode code points of the string value as individual strings.
Description
Strings are iterated by Unicode code points. This means grapheme clusters will be split, but surrogate pairs will be preserved.
// "Backhand Index Pointing Right: Dark Skin Tone"
[..."👉🏿"]; // ['👉', '🏿']
// splits into the basic "Backhand Index Pointing Right" emoji and
// the "Dark skin tone" emoji
// "Family: Man, Boy"
[..."👨👦"]; // [ '👨', '', '👦' ]
// splits into the "Man" and "Boy" emoji, joined by a ZWJ
Examples
Iteration using for...of loop
Note that you seldom need to call this method directly. The existence of the @@iterator method makes strings iterable, and iterating syntaxes like the for...of loop automatically call this method to obtain the iterator to loop over.
const str = "A\uD835\uDC68B\uD835\uDC69C\uD835\uDC6A";
for (const v of str) {
console.log(v);
}
// "A"
// "\uD835\uDC68"
// "B"
// "\uD835\uDC69"
// "C"
// "\uD835\uDC6A"
Manually hand-rolling the iterator
You may still manually call the next() method of the returned iterator object to achieve maximum control over the iteration process.
const str = "A\uD835\uDC68";
const strIter = str[Symbol.iterator]();
console.log(strIter.next().value); // "A"
console.log(strIter.next().value); // "\uD835\uDC68"