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Dynamically add content to make <sup>s copy-paste safe (#517)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,71 @@ | ||
| 'use strict'; | ||
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| // Update superscripts to not suffer misinterpretation when copied and pasted as plain text. | ||
| // For example, | ||
| // * Replace `10<sup>3</sup>` with | ||
| // `10<span aria-hidden="true">**</span><sup>3</sup>` | ||
| // so it gets pasted as `10**3` rather than `103`. | ||
| // * Replace `10<sup>-<var>x</var></sup>` with | ||
| // `10<span aria-hidden="true">**</span><sup>-<var>x</var></sup>` | ||
| // so it gets pasted as `10**-x` rather than `10-x`. | ||
| // * Replace `2<sup><var>a</var> + 1</sup>` with | ||
| // `2<span …>**(</span><sup><var>a</var> + 1</sup><span …>)</span>` | ||
| // so it gets pasted as `2**(a + 1)` rather than `2a + 1`. | ||
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| function makeExponentPlainTextSafe(sup) { | ||
| // Change a <sup> only if it appears to be an exponent: | ||
| // * text-only and contains only mathematical content (not e.g. `1<sup>st</sup>`) | ||
| // * contains only <var>s and internal links (e.g. | ||
| // `2<sup><emu-xref><a href="#ℝ">ℝ</a></emu-xref>(_y_)</sup>`) | ||
| const isText = [...sup.childNodes].every(node => node.nodeType === 3); | ||
| const text = sup.textContent; | ||
| if (isText) { | ||
| if (!/^[0-9. 𝔽ℝℤ()=*×/÷±+\u2212-]+$/u.test(text)) { | ||
| return; | ||
| } | ||
| } else { | ||
| if (sup.querySelector('*:not(var, emu-xref, :scope emu-xref a)')) { | ||
| return; | ||
| } | ||
| } | ||
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| let prefix = '**'; | ||
| let suffix = ''; | ||
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| // Add wrapping parentheses unless they are already present | ||
| // or this is a simple (possibly signed) integer or single-variable exponent. | ||
| const skipParens = | ||
| /^[±+\u2212-]?(?:[0-9]+|\p{ID_Start}\p{ID_Continue}*)$/u.test(text) || | ||
| // Split on parentheses and remember them; the resulting parts must | ||
| // start and end empty (i.e., with open/close parentheses) | ||
| // and increase depth to 1 only at the first parenthesis | ||
| // to e.g. wrap `(a+1)*(b+1)` but not `((a+1)*(b+1))`. | ||
| text | ||
| .trim() | ||
| .split(/([()])/g) | ||
| .reduce((depth, s, i, parts) => { | ||
| if (s === '(') { | ||
| return depth > 0 || i === 1 ? depth + 1 : NaN; | ||
| } else if (s === ')') { | ||
| return depth > 0 ? depth - 1 : NaN; | ||
| } else if (s === '' || (i > 0 && i < parts.length - 1)) { | ||
| return depth; | ||
| } | ||
| return NaN; | ||
| }, 0) === 0; | ||
| if (!skipParens) { | ||
| prefix += '('; | ||
| suffix += ')'; | ||
| } | ||
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| sup.insertAdjacentHTML('beforebegin', `<span aria-hidden="true">${prefix}</span>`); | ||
| if (suffix) { | ||
| sup.insertAdjacentHTML('afterend', `<span aria-hidden="true">${suffix}</span>`); | ||
| } | ||
| } | ||
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| document.addEventListener('DOMContentLoaded', () => { | ||
| document.querySelectorAll('sup:not(.text)').forEach(sup => { | ||
| makeExponentPlainTextSafe(sup); | ||
| }); | ||
| }); |
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