55 lines
1.6 KiB
Plaintext
55 lines
1.6 KiB
Plaintext
/*! https://mths.be/codepointat v0.2.0 by @mathias */
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if (!String.prototype.codePointAt) {
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(function() {
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'use strict'; // needed to support `apply`/`call` with `undefined`/`null`
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var defineProperty = (function() {
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// IE 8 only supports `Object.defineProperty` on DOM elements
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try {
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var object = {};
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var $defineProperty = Object.defineProperty;
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var result = $defineProperty(object, object, object) && $defineProperty;
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} catch(error) {}
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return result;
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}());
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var codePointAt = function(position) {
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if (this == null) {
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throw TypeError();
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}
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var string = String(this);
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var size = string.length;
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// `ToInteger`
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var index = position ? Number(position) : 0;
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if (index != index) { // better `isNaN`
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index = 0;
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}
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// Account for out-of-bounds indices:
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if (index < 0 || index >= size) {
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return undefined;
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}
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// Get the first code unit
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var first = string.charCodeAt(index);
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var second;
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if ( // check if it’s the start of a surrogate pair
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first >= 0xD800 && first <= 0xDBFF && // high surrogate
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size > index + 1 // there is a next code unit
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) {
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second = string.charCodeAt(index + 1);
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if (second >= 0xDC00 && second <= 0xDFFF) { // low surrogate
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// https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
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return (first - 0xD800) * 0x400 + second - 0xDC00 + 0x10000;
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}
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}
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return first;
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};
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if (defineProperty) {
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defineProperty(String.prototype, 'codePointAt', {
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'value': codePointAt,
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'configurable': true,
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'writable': true
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});
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} else {
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String.prototype.codePointAt = codePointAt;
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}
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}());
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}
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