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35 lines
752 B
35 lines
752 B
'use strict'
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var uglify = require('uglify-js')
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var lastSRC = '(null)'
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var lastRes = true
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module.exports = isConstant
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function isConstant(src) {
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src = '(' + src + ')'
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if (lastSRC === src) return lastRes
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lastSRC = src
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try {
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return lastRes = (detect(src).length === 0)
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} catch (ex) {
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return lastRes = false
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}
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}
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isConstant.isConstant = isConstant
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isConstant.toConstant = toConstant
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function toConstant(src) {
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if (!isConstant(src)) throw new Error(JSON.stringify(src) + ' is not constant.')
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return Function('return (' + src + ')')()
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}
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function detect(src) {
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var ast = uglify.parse(src.toString())
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ast.figure_out_scope()
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var globals = ast.globals
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.map(function (node, name) {
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return name
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})
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return globals
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}
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