| 1 | const parse = require('./parse')
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| 2 | const eq = require('./eq')
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| 3 |
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| 4 | const diff = (version1, version2) => {
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| 5 | if (eq(version1, version2)) {
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| 6 | return null
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| 7 | } else {
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| 8 | const v1 = parse(version1)
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| 9 | const v2 = parse(version2)
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| 10 | const hasPre = v1.prerelease.length || v2.prerelease.length
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| 11 | const prefix = hasPre ? 'pre' : ''
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| 12 | const defaultResult = hasPre ? 'prerelease' : ''
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| 13 | for (const key in v1) {
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| 14 | if (key === 'major' || key === 'minor' || key === 'patch') {
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| 15 | if (v1[key] !== v2[key]) {
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| 16 | return prefix + key
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| 17 | }
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| 18 | }
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| 19 | }
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| 20 | return defaultResult
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| 21 | }
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| 22 | }
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| 23 | module.exports = diff
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