initial commit

.gitignore

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+.nyc_output

.travis.yml

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+language: node_js
+node_js:
+  - "4"
+  - "5"
+  - "iojs"
+  - "iojs-v1"
+  - "iojs-v2"
+sudo: false

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2016 Evan Lucas
+
+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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+# map-util
+
+[![Build Status](https://travis-ci.org/evanlucas/map-util.svg)](https://travis-ci.org/evanlucas/map-util)
+[![Coverage Status](https://coveralls.io/repos/evanlucas/map-util/badge.svg?branch=master&service=github)](https://coveralls.io/github/evanlucas/map-util?branch=master)
+
+Simple set of utilities that make getting the previous or next value in a map
+easier.
+
+## Install
+
+```bash
+$ npm install [--save] map-util
+```
+
+## Usage
+
+```js
+'use strict'
+
+const nextVal = require('map-util').nextVal
+const prevVal = require('map-util').prevVal
+
+const map = new Map()
+map.set('1', '1')
+map.set('2', '2')
+
+nextVal('1', map) // => '2'
+nextVal('2', map) // => null
+// If we want to wrap around:
+nextVal('2', map, true) // => '1'
+
+prevVal('2', map) // => '1'
+prevVal('1', map) // => null
+// If we want to wrap around:
+prevVal('1', map, true) // => '2'
+```
+
+## Test
+
+```bash
+$ npm test
+```
+
+## Author
+
+Evan Lucas
+
+## License
+
+MIT (See `LICENSE` for more info)

index.js

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+'use strict'
+
+exports.nextVal = require('./lib/next-val')
+exports.prevVal = require('./lib/prev-val')

lib/next-val.js

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+'use strict'
+
+module.exports = nextVal
+
+function nextVal(search, map, wrap) {
+  if (!(map instanceof Map)) {
+    throw new TypeError('map must be a Map')
+  }
+
+  if (map.size < 2) {
+    return null
+  }
+
+  let found = false
+
+  for (const item of map.values()) {
+    if (found) {
+      return item
+    }
+
+    if (search === item) {
+      found = true
+    }
+  }
+
+  // this means we tried to get the next value of the last value,
+  // so return the first
+  if (wrap && found) {
+    return map.values().next().value
+  }
+
+  // could not find item
+  return null
+}

lib/prev-val.js

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+'use strict'
+
+module.exports = prevVal
+
+const lastSymbol = Symbol('last')
+
+function prevVal(search, map, wrap) {
+  if (!(map instanceof Map)) {
+    throw new TypeError('map must be a Map')
+  }
+
+  if (map.size < 2) {
+    return null
+  }
+
+  let prev = null
+  let last = null
+
+  for (const item of map.values()) {
+    if (item === search) {
+      if (prev === null) {
+        last = lastSymbol
+        continue
+      }
+      return prev
+    }
+
+    prev = item
+    if (last === lastSymbol) {
+      last = item
+    }
+  }
+
+  if (wrap && last) {
+    return last
+  }
+
+
+  return null
+}

package.json

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+{
+  "name": "map-util",
+  "version": "1.0.0",
+  "description": "Utilities that make getting prev/next values in a map easier",
+  "main": "index.js",
+  "scripts": {
+    "test": "tap test.js --cov"
+  },
+  "dependencies": {},
+  "devDependencies": {
+    "tap": "~5.7.0"
+  },
+  "license": "MIT",
+  "author": "Evan Lucas <evanlucas@me.com>",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/evanlucas/map-util"
+  },
+  "homepage": "https://github.com/evanlucas/map-util",
+  "bugs": {
+    "url": "https://github.com/evanlucas/map-util/issues"
+  }
+}

test.js

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+'use strict'
+
+const test = require('tap').test
+const utils = require('./')
+
+test('nextVal', (t) => {
+  t.throws(function() {
+    t.equal(utils.nextVal())
+  }, /map must be a Map/)
+
+  const m = new Map()
+  t.equal(utils.nextVal(null, m), null)
+  m.set('1', '1')
+  t.equal(utils.nextVal(null, m), null)
+
+  m.set('2', '2')
+  t.equal(utils.nextVal('2', m), null)
+  t.equal(utils.nextVal('2', m, true), '1')
+  t.equal(utils.nextVal('1', m), '2')
+  t.equal(utils.nextVal('3', m), null)
+  t.end()
+})
+
+test('prevVal', (t) => {
+  t.throws(function() {
+    t.equal(utils.prevVal())
+  }, /map must be a Map/)
+
+  const m = new Map()
+  t.equal(utils.prevVal(null, m), null)
+  m.set('1', '1')
+  t.equal(utils.prevVal(null, m), null)
+
+  m.set('2', '2')
+  t.equal(utils.prevVal('2', m), '1')
+  t.equal(utils.prevVal('1', m, true), '2')
+  t.equal(utils.prevVal('1', m), null)
+  t.equal(utils.prevVal('3', m), null)
+  t.end()
+})