81 lines
1.4 KiB
JavaScript
81 lines
1.4 KiB
JavaScript
'use strict'
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/**
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* @param {string | RegExp} a
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* @param {string | RegExp} b
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* @param {string} str
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*/
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function balanced(a, b, str) {
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if (a instanceof RegExp) a = maybeMatch(a, str)
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if (b instanceof RegExp) b = maybeMatch(b, str)
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const r = range(a, b, str)
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return (
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r && {
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start: r[0],
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end: r[1],
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pre: str.slice(0, r[0]),
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body: str.slice(r[0] + a.length, r[1]),
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post: str.slice(r[1] + b.length)
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}
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)
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}
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/**
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* @param {RegExp} reg
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* @param {string} str
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*/
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function maybeMatch(reg, str) {
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const m = str.match(reg)
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return m ? m[0] : null
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}
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balanced.range = range
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/**
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* @param {string} a
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* @param {string} b
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* @param {string} str
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*/
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function range(a, b, str) {
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let begs, beg, left, right, result
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let ai = str.indexOf(a)
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let bi = str.indexOf(b, ai + 1)
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let i = ai
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if (ai >= 0 && bi > 0) {
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if (a === b) {
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return [ai, bi]
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}
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begs = []
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left = str.length
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while (i >= 0 && !result) {
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if (i === ai) {
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begs.push(i)
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ai = str.indexOf(a, i + 1)
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} else if (begs.length === 1) {
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result = [begs.pop(), bi]
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} else {
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beg = begs.pop()
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if (beg < left) {
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left = beg
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right = bi
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}
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bi = str.indexOf(b, i + 1)
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}
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i = ai < bi && ai >= 0 ? ai : bi
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}
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if (begs.length) {
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result = [left, right]
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}
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}
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return result
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}
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module.exports = balanced |