time-to-botec

README.md (10645B)

---

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 # Doubly Linked List
 
 > Doubly linked list constructor.
 
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 <section class="intro">
 
 </section>
 
 <!-- /.intro -->
 
 <!-- Package usage documentation. -->
 
 <section class="usage">
 
 ## Usage
 
 ```javascript
 var doublyLinkedList = require( '@stdlib/utils/doubly-linked-list' );
 ```
 
 #### doublyLinkedList()
 
 Returns a new doubly linked list instance.
 
 ```javascript
 var list = doublyLinkedList();
 // returns <DoublyLinkedList>
 ```
 
 ##### list.clear()
 
 Clears a list.
 
 ```javascript
 var list = doublyLinkedList();
 // returns <DoublyLinkedList>
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Peek at the first value:
 var v = list.first().value;
 // returns 'foo'
 
 // Examine the list length:
 var len = list.length;
 // returns 2
 
 // Clear all list items:
 list.clear();
 
 // Peek at the first value:
 v = list.first();
 // returns undefined
 
 // Examine the list length:
 len = list.length;
 // returns 0
 ```
 
 ##### list.first()
 
 Returns the first `node`. If the list is currently empty, the returned value is `undefined`.
 
 ```javascript
 var list = doublyLinkedList();
 // returns <DoublyLinkedList>
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Peek at the first value:
 var v = list.first().value;
 // returns 'foo'
 ```
 
 ##### list.insert( node, value\[, location] )
 
 Inserts a `value` into the list either before or after a provided list `node`.
 
 ```javascript
 var list = doublyLinkedList();
 // returns <DoublyLinkedList>
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' ).push( 'beep' );
 
 // Determine the list length:
 var len = list.length;
 // returns 3
 
 // Get the second node:
 var node = list.first().next;
 
 // Insert a value after the second node:
 list.insert( node, 'boop' );
 
 // Determine the list length:
 len = list.length;
 // returns 4
 
 // Return a list of values:
 var values = list.toArray();
 // returns [ 'foo', 'bar', 'boop', 'beep' ]
 ```
 
 The method supports the following insertion locations:
 
 -   `'before'`: insert a `value` into the list **before** a provided list `node`.
 -   `'after'`: insert a `value` into the list **after** a provided list `node`.
 
 By default, the method inserts a `value` into the list **after** a provided list `node`. To insert a value **before** a provided list `node`, invoke the method with the `location` argument equal to `'before'`.
 
 ```javascript
 var list = doublyLinkedList();
 // returns <DoublyLinkedList>
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' ).push( 'beep' );
 
 // Determine the list length:
 var len = list.length;
 // returns 3
 
 // Get the second node:
 var node = list.first().next;
 
 // Insert a value before the second node:
 list.insert( node, 'boop', 'before' );
 
 // Determine the list length:
 len = list.length;
 // returns 4
 
 // Return a list of values:
 var values = list.toArray();
 // returns [ 'foo', 'boop', 'bar', 'beep' ]
 ```
 
 ##### list.iterator( \[direction] )
 
 Returns an iterator for iterating over a list. If an environment supports `Symbol.iterator`, the returned iterator is iterable.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Create an iterator:
 var it = list.iterator();
 
 // Iterate over the list...
 var v = it.next().value;
 // returns 'foo'
 
 v = it.next().value;
 // returns 'bar'
 
 var bool = it.next().done;
 // returns true
 ```
 
 The method supports the following iteration directions:
 
 -   `'forward'`: iterate over a list from the first value until the last value.
 -   `'reverse'`: iterate over a list from the last value until the first value.
 
 By default, the method returns an iterator which iterates over a list from the first value until the last value. To return an iterator which iterates in reverse order, invoke the method with the `direction` argument equal to `'reverse'`.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Create an iterator:
 var it = list.iterator( 'reverse' );
 
 // Iterate over the list...
 var v = it.next().value;
 // returns 'bar'
 
 v = it.next().value;
 // returns 'foo'
 
 var bool = it.next().done;
 // returns true
 ```
 
 **Note**: in order to prevent confusion arising from list mutation during iteration, a returned iterator **always** iterates over a list "snapshot", which is defined as the list of list elements at the time of `list.iterator()` invocation.
 
 ##### list.last()
 
 Returns the last `node`. If the list is currently empty, the returned value is `undefined`.
 
 ```javascript
 var list = doublyLinkedList();
 // returns <DoublyLinkedList>
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Peek at the last value:
 var v = list.last().value;
 // returns 'bar'
 ```
 
 ##### list.length
 
 List length.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Examine the initial list length:
 var len = list.length;
 // returns 0
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Retrieve the current list length:
 len = list.length;
 // returns 2
 ```
 
 ##### list.pop()
 
 Removes a value from the end of the list. If the list is currently empty, the returned value is `undefined`.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Remove the last value:
 var v = list.pop();
 // returns 'bar'
 
 // Add a new value to the list:
 list.push( 'beep' );
 
 // Remove the last value:
 v = list.pop();
 // returns 'beep'
 ```
 
 ##### list.push( value )
 
 Adds a value to the end of the list.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Remove the last value:
 var v = list.pop();
 // returns 'bar'
 
 // Add a new value to the list:
 list.push( 'beep' );
 
 // Remove the last value:
 v = list.pop();
 // returns 'beep'
 ```
 
 ##### list.remove( node )
 
 Removes a `node` from the list.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' ).push( 'beep' );
 
 // Determine the list length:
 var len = list.length;
 // returns 3
 
 // Get the second node:
 var node = list.first().next;
 
 // Remove the second node:
 var v = list.remove( node );
 // returns 'bar'
 
 // Determine the list length:
 len = list.length;
 // returns 2
 ```
 
 ##### list.shift()
 
 Removes a value from the beginning of the list. If the list is currently empty, the returned value is `undefined`.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Remove the first value:
 var v = list.shift();
 // returns 'foo'
 
 // Add a new value to the list:
 list.push( 'beep' );
 
 // Remove the first value:
 v = list.shift();
 // returns 'bar'
 ```
 
 ##### list.toArray()
 
 Returns an array of list values.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Get an array of list values:
 var vals = list.toArray();
 // returns [ 'foo', 'bar' ]
 ```
 
 ##### list.toJSON()
 
 Serializes a list as JSON.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.push( 'foo' ).push( 'bar' );
 
 // Serialize to JSON:
 var o = list.toJSON();
 // returns { 'type': 'doubly-linked-list', 'data': [ 'foo', 'bar' ] }
 ```
 
 **Note**: `JSON.stringify()` implicitly calls this method when stringifying a list instance.
 
 ##### list.unshift( value )
 
 Adds a value to the beginning of the list.
 
 ```javascript
 var list = doublyLinkedList();
 
 // Add values to the list:
 list.unshift( 'foo' ).unshift( 'bar' );
 
 // Remove the last value:
 var v = list.pop();
 // returns 'foo'
 
 // Add a new value to the list:
 list.unshift( 'beep' );
 
 // Remove the last value:
 v = list.pop();
 // returns 'bar'
 ```
 
 </section>
 
 <!-- /.usage -->
 
 <!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
 
 <section class="notes">
 
 ## Notes
 
 -   To manually traverse a list, use list node `next` and `prev` properties.
 
     ```javascript
     var list = doublyLinkedList();
 
     // Add values to the list:
     list.push( 'foo' ).push( 'bar' ).push( 'beep' ).push( 'boop' );
 
     // Get the first list node:
     var n = list.first();
 
     // Walk the list forward...
     while ( n ) {
         console.log( n.value );
         n = n.next;
     }
 
     // Get the last list node:
     n = list.last();
 
     // Walk the list backward...
     while ( n ) {
         console.log( n.value );
         n = n.prev;
     }
     ```
 
 </section>
 
 <!-- /.notes -->
 
 <!-- Package usage examples. -->
 
 <section class="examples">
 
 ## Examples
 
 <!-- eslint no-undef: "error" -->
 
 ```javascript
 var doublyLinkedList = require( '@stdlib/utils/doubly-linked-list' );
 
 var list;
 var iter;
 var len;
 var v;
 var i;
 
 // Create a new doubly linked list:
 list = doublyLinkedList();
 
 // Add some values to the list:
 list.push( 'foo' );
 list.push( 'bar' );
 list.push( 'beep' );
 list.push( 'boop' );
 
 // Peek at the first and last list values:
 v = list.first().value;
 // returns 'foo'
 
 v = list.last().value;
 // returns 'boop'
 
 // Inspect the list length:
 len = list.length;
 // returns 4
 
 // Remove the last list value:
 v = list.pop();
 // returns 'boop'
 
 // Inspect the list length:
 len = list.length;
 // returns 3
 
 // Iterate over the list:
 iter = list.iterator();
 for ( i = 0; i < len; i++ ) {
     console.log( 'List value #%d: %s', i+1, iter.next().value );
 }
 
 // Clear the list:
 list.clear();
 
 // Inspect the list length:
 len = list.length;
 // returns 0
 ```
 
 </section>
 
 <!-- /.examples -->
 
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