Initial Code

.gitattributes

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+# Auto detect text files and perform LF normalization
+* text=auto
+
+# Custom for Visual Studio
+*.cs     diff=csharp
+*.sln    merge=union
+*.csproj merge=union
+*.vbproj merge=union
+*.fsproj merge=union
+*.dbproj merge=union
+
+# Standard to msysgit
+*.doc	 diff=astextplain
+*.DOC	 diff=astextplain
+*.docx diff=astextplain
+*.DOCX diff=astextplain
+*.dot  diff=astextplain
+*.DOT  diff=astextplain
+*.pdf  diff=astextplain
+*.PDF	 diff=astextplain
+*.rtf	 diff=astextplain
+*.RTF	 diff=astextplain

.gitignore

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+lib-cov
+*.seed
+*.log
+*.csv
+*.dat
+*.out
+*.pid
+*.gz
+pids
+logs
+results
+npm-debug.log
+node_modules

.travis.yml

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+language: node_js
+node_js:
+  - "0.8"
+  - "0.10"

LICENSE

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+Copyright (c) 2013 Forbes Lindesay
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# constantinople
+
+Determine whether a JavaScript expression evaluates to a constant (using UglifyJS).  Here it is assumed to be safe to underestimate how constant something is.
+
+[![Build Status](https://travis-ci.org/ForbesLindesay/constantinople.png?branch=master)](https://travis-ci.org/ForbesLindesay/constantinople)
+[![Dependency Status](https://gemnasium.com/ForbesLindesay/constantinople.png)](https://gemnasium.com/ForbesLindesay/constantinople)
+[![NPM version](https://badge.fury.io/js/constantinople.png)](http://badge.fury.io/js/constantinople)
+
+## Installation
+
+    npm install constantinople
+
+## Usage
+
+```js
+var isConstant = require('constantinople')
+
+if (isConstant('"foo" + 5')) {
+  console.dir(isConstant.toConstant('"foo" + 5'))
+}
+```
+
+## API
+
+### isConstant(src)
+
+Returns `true` if `src` evaluates to a constant, `false` otherwise.  It will also return `false` if there is a syntax error, which makes it safe to use on potentially ES6 code.
+
+### toConstant(src)
+
+Returns the value resulting from evaluating `src`.  This method throws an error if the expression is not constant.  e.g. `toConstant("Math.random()")` would throw an error.
+
+## License
+
+  MIT

index.js

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

package.json

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+{
+  "name": "constantinople",
+  "version": "0.0.0",
+  "description": "Determine whether a JavaScript expression evaluates to a constant (using UglifyJS)",
+  "keywords": [],
+  "dependencies": {
+    "uglify-js": "~2.3.6"
+  },
+  "devDependencies": {
+    "mocha": "*"
+  },
+  "scripts": {
+    "test": "mocha -R spec"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/ForbesLindesay/constantinople.git"
+  },
+  "author": "ForbesLindesay",
+  "license": "MIT"
+}

test/index.js

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+'use strict'
+
+var assert = require('assert')
+var constaninople = require('../')
+
+describe('isConstant(src)', function () {
+  it('handles "[5 + 3 + 10]"', function () {
+    assert(constaninople.isConstant('[5 + 3 + 10]') === true)
+  })
+  it('handles "/[a-z]/.test(\'a\')"', function () {
+    assert(constaninople.isConstant('/[a-z]/.test(\'a\')') === true)
+  })
+  it('handles "Math.random()"', function () {
+    assert(constaninople.isConstant('Math.random()') === false)
+  })
+  it('handles "Math.random("', function () {
+    assert(constaninople.isConstant('Math.random(') === false)
+  })
+})
+
+
+describe('toConstant(src)', function () {
+  it('handles "[5 + 3 + 10]"', function () {
+    assert.deepEqual(constaninople.toConstant('[5 + 3 + 10]'), [5 + 3 + 10])
+  })
+  it('handles "/[a-z]/.test(\'a\')"', function () {
+    assert(constaninople.toConstant('/[a-z]/.test(\'a\')') === true)
+  })
+  it('handles "Math.random()"', function () {
+    try {
+      constaninople.toConstant('Math.random()')
+    } catch (ex) {
+      return
+    }
+    assert(false, 'Math.random() should result in an error')
+  })
+  it('handles "Math.random("', function () {
+    try {
+      constaninople.toConstant('Math.random(')
+    } catch (ex) {
+      return
+    }
+    assert(false, 'Math.random( should result in an error')
+  })
+})