These functions are used by xduce to create iterators for strings in pre-ES2015 environments. String iterators in ES2015+ account for double-width characters in the Basic Multilingual Plane, returning those double-wide characters as one iterator value. Older environments do not do this; double-width characters would in that case be returned as two distinct characters, but for Xduce's use of these functions.
Note that the built-in charAt and length do not take double-width characters into account even in ES2015+
environments even though iterators do. These functions are still useful as utility functions in any environment.
Methods
(static) charAt(str, index) → {string}
- Source:
Returns the character at a particular index in a string, taking double-width BMP characters into account.
This is a BMP version of the standard JavaScript string.charAt function. The index is adjusted to account for
double-width characters in the input string, and if the resulting character is double-width, it will be returned as a
two-character string. The second half of these double-width characters don't get assigned an index at all, so it
works seemlessly between character widths.
Parameters:
| Name | Type | Description |
|---|---|---|
str |
string | The input string whose character at the given index is sought. |
index |
number | The index in the input string of the character being sought. |
Returns:
The character at the given index in the provided string. If this character is a BMP character, the full character will be returned as a two-character string.
- Type
- string
(static) length(str) → {number}
- Source:
Calculates the length of a string, taking double-width BMP characters into account.
Since this function takes double-width characters into account and the build in string length property does not,
it is entirely possible for this function to provide a different result than querying the same string's length
property.
Parameters:
| Name | Type | Description |
|---|---|---|
str |
string | The string whose length is being determined. |
Returns:
The number of characters in the string, counting double-width BMP characters as single characters.
- Type
- number