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