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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/charCodeAt#Fixing_charCodeAt()_to_handle_non-Basic-Multilingual-Plane_characters_if_their_presence_earlier_in_the_string_is_known
function knownCharCodeAt(givenString, index) {
const str = `${givenString}`;
const end = str.length;
const surrogatePairs = /[\uD800-\uDBFF][\uDC00-\uDFFF]/g;
let idx = index;
while ((surrogatePairs.exec(str)) != null) {
const li = surrogatePairs.lastIndex;
if (li - 2 < idx) {
idx += 1;
} else {
break;
}
}
if (idx >= end || idx < 0) {
return NaN;
}
const code = str.charCodeAt(idx);
let high;
let low;
if (code >= 0xD800 && code <= 0xDBFF) {
high = code;
low = str.charCodeAt(idx + 1);
// Go one further, since one of the "characters" is part of a surrogate pair
return ((high - 0xD800) * 0x400) + (low - 0xDC00) + 0x10000;
}
return code;
}
// See http://stackoverflow.com/a/38901550/796832
// ES5/PhantomJS compatible version of spreading a string
//
// [...'foo'] -> ['f', 'o', 'o']
// [...'🖐🏿'] -> ['🖐', '🏿']
function spreadString(str) {
const arr = [];
let i = 0;
while (!isNaN(knownCharCodeAt(str, i))) {
const codePoint = knownCharCodeAt(str, i);
arr.push(String.fromCodePoint(codePoint));
i += 1;
}
return arr;
}
module.exports = spreadString;
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