src/text-utils.js
const isHighSurrogate = charCode => charCode >= 0xd800 && charCode <= 0xdbff;
const isLowSurrogate = charCode => charCode >= 0xdc00 && charCode <= 0xdfff;
const isVariationSelector = charCode =>
charCode >= 0xfe00 && charCode <= 0xfe0f;
const isCombiningCharacter = charCode =>
(charCode >= 0x0300 && charCode <= 0x036f) ||
(charCode >= 0x1ab0 && charCode <= 0x1aff) ||
(charCode >= 0x1dc0 && charCode <= 0x1dff) ||
(charCode >= 0x20d0 && charCode <= 0x20ff) ||
(charCode >= 0xfe20 && charCode <= 0xfe2f);
// Are the given character codes a high/low surrogate pair?
//
// * `charCodeA` The first character code {Number}.
// * `charCode2` The second character code {Number}.
//
// Return a {Boolean}.
const isSurrogatePair = (charCodeA, charCodeB) =>
isHighSurrogate(charCodeA) && isLowSurrogate(charCodeB);
// Are the given character codes a variation sequence?
//
// * `charCodeA` The first character code {Number}.
// * `charCode2` The second character code {Number}.
//
// Return a {Boolean}.
const isVariationSequence = (charCodeA, charCodeB) =>
!isVariationSelector(charCodeA) && isVariationSelector(charCodeB);
// Are the given character codes a combined character pair?
//
// * `charCodeA` The first character code {Number}.
// * `charCode2` The second character code {Number}.
//
// Return a {Boolean}.
const isCombinedCharacter = (charCodeA, charCodeB) =>
!isCombiningCharacter(charCodeA) && isCombiningCharacter(charCodeB);
// Is the character at the given index the start of high/low surrogate pair
// a variation sequence, or a combined character?
//
// * `string` The {String} to check for a surrogate pair, variation sequence,
// or combined character.
// * `index` The {Number} index to look for a surrogate pair, variation
// sequence, or combined character.
//
// Return a {Boolean}.
const isPairedCharacter = (string, index = 0) => {
const charCodeA = string.charCodeAt(index);
const charCodeB = string.charCodeAt(index + 1);
return (
isSurrogatePair(charCodeA, charCodeB) ||
isVariationSequence(charCodeA, charCodeB) ||
isCombinedCharacter(charCodeA, charCodeB)
);
};
const IsJapaneseKanaCharacter = charCode =>
charCode >= 0x3000 && charCode <= 0x30ff;
const isCJKUnifiedIdeograph = charCode =>
charCode >= 0x4e00 && charCode <= 0x9fff;
const isFullWidthForm = charCode =>
(charCode >= 0xff01 && charCode <= 0xff5e) ||
(charCode >= 0xffe0 && charCode <= 0xffe6);
const isDoubleWidthCharacter = character => {
const charCode = character.charCodeAt(0);
return (
IsJapaneseKanaCharacter(charCode) ||
isCJKUnifiedIdeograph(charCode) ||
isFullWidthForm(charCode)
);
};
const isHalfWidthCharacter = character => {
const charCode = character.charCodeAt(0);
return (
(charCode >= 0xff65 && charCode <= 0xffdc) ||
(charCode >= 0xffe8 && charCode <= 0xffee)
);
};
const isKoreanCharacter = character => {
const charCode = character.charCodeAt(0);
return (
(charCode >= 0xac00 && charCode <= 0xd7a3) ||
(charCode >= 0x1100 && charCode <= 0x11ff) ||
(charCode >= 0x3130 && charCode <= 0x318f) ||
(charCode >= 0xa960 && charCode <= 0xa97f) ||
(charCode >= 0xd7b0 && charCode <= 0xd7ff)
);
};
const isCJKCharacter = character =>
isDoubleWidthCharacter(character) ||
isHalfWidthCharacter(character) ||
isKoreanCharacter(character);
const isWordStart = (previousCharacter, character) =>
(previousCharacter === ' ' ||
previousCharacter === '\t' ||
previousCharacter === '-' ||
previousCharacter === '/') &&
(character !== ' ' && character !== '\t');
const isWrapBoundary = (previousCharacter, character) =>
isWordStart(previousCharacter, character) || isCJKCharacter(character);
// Does the given string contain at least surrogate pair, variation sequence,
// or combined character?
//
// * `string` The {String} to check for the presence of paired characters.
//
// Returns a {Boolean}.
const hasPairedCharacter = string => {
let index = 0;
while (index < string.length) {
if (isPairedCharacter(string, index)) {
return true;
}
index++;
}
return false;
};
module.exports = {
isPairedCharacter,
hasPairedCharacter,
isDoubleWidthCharacter,
isHalfWidthCharacter,
isKoreanCharacter,
isWrapBoundary
};