204 lines
4.6 KiB
Markdown
204 lines
4.6 KiB
Markdown
# yallist
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Yet Another Linked List
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There are many doubly-linked list implementations like it, but this
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one is mine.
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For when an array would be too big, and a Map can't be iterated in
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reverse order.
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[](https://travis-ci.org/isaacs/yallist) [](https://coveralls.io/github/isaacs/yallist)
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## basic usage
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```javascript
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var yallist = require('yallist')
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var myList = yallist.create([1, 2, 3])
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myList.push('foo')
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myList.unshift('bar')
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// of course pop() and shift() are there, too
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console.log(myList.toArray()) // ['bar', 1, 2, 3, 'foo']
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myList.forEach(function (k) {
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// walk the list head to tail
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})
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myList.forEachReverse(function (k, index, list) {
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// walk the list tail to head
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})
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var myDoubledList = myList.map(function (k) {
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return k + k
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})
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// now myDoubledList contains ['barbar', 2, 4, 6, 'foofoo']
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// mapReverse is also a thing
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var myDoubledListReverse = myList.mapReverse(function (k) {
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return k + k
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}) // ['foofoo', 6, 4, 2, 'barbar']
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var reduced = myList.reduce(function (set, entry) {
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set += entry
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return set
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}, 'start')
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console.log(reduced) // 'startfoo123bar'
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```
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## api
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The whole API is considered "public".
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Functions with the same name as an Array method work more or less the
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same way.
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There's reverse versions of most things because that's the point.
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### Yallist
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Default export, the class that holds and manages a list.
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Call it with either a forEach-able (like an array) or a set of
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arguments, to initialize the list.
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The Array-ish methods all act like you'd expect. No magic length,
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though, so if you change that it won't automatically prune or add
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empty spots.
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### Yallist.create(..)
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Alias for Yallist function. Some people like factories.
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#### yallist.head
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The first node in the list
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#### yallist.tail
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The last node in the list
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#### yallist.length
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The number of nodes in the list. (Change this at your peril. It is
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not magic like Array length.)
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#### yallist.toArray()
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Convert the list to an array.
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#### yallist.forEach(fn, [thisp])
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Call a function on each item in the list.
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#### yallist.forEachReverse(fn, [thisp])
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Call a function on each item in the list, in reverse order.
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#### yallist.get(n)
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Get the data at position `n` in the list. If you use this a lot,
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probably better off just using an Array.
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#### yallist.getReverse(n)
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Get the data at position `n`, counting from the tail.
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#### yallist.map(fn, thisp)
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Create a new Yallist with the result of calling the function on each
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item.
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#### yallist.mapReverse(fn, thisp)
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Same as `map`, but in reverse.
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#### yallist.pop()
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Get the data from the list tail, and remove the tail from the list.
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#### yallist.push(item, ...)
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Insert one or more items to the tail of the list.
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#### yallist.reduce(fn, initialValue)
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Like Array.reduce.
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#### yallist.reduceReverse
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Like Array.reduce, but in reverse.
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#### yallist.reverse
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Reverse the list in place.
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#### yallist.shift()
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Get the data from the list head, and remove the head from the list.
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#### yallist.slice([from], [to])
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Just like Array.slice, but returns a new Yallist.
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#### yallist.sliceReverse([from], [to])
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Just like yallist.slice, but the result is returned in reverse.
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#### yallist.toArray()
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Create an array representation of the list.
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#### yallist.toArrayReverse()
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Create a reversed array representation of the list.
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#### yallist.unshift(item, ...)
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Insert one or more items to the head of the list.
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#### yallist.unshiftNode(node)
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Move a Node object to the front of the list. (That is, pull it out of
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wherever it lives, and make it the new head.)
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If the node belongs to a different list, then that list will remove it
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first.
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#### yallist.pushNode(node)
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Move a Node object to the end of the list. (That is, pull it out of
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wherever it lives, and make it the new tail.)
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If the node belongs to a list already, then that list will remove it
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first.
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#### yallist.removeNode(node)
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Remove a node from the list, preserving referential integrity of head
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and tail and other nodes.
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Will throw an error if you try to have a list remove a node that
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doesn't belong to it.
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### Yallist.Node
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The class that holds the data and is actually the list.
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Call with `var n = new Node(value, previousNode, nextNode)`
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Note that if you do direct operations on Nodes themselves, it's very
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easy to get into weird states where the list is broken. Be careful :)
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#### node.next
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The next node in the list.
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#### node.prev
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The previous node in the list.
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#### node.value
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The data the node contains.
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#### node.list
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The list to which this node belongs. (Null if it does not belong to
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any list.)
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