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Refactor to improve bundle size
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@wooorm
wooorm committed Jan 19, 2021
1 parent b79ba3e commit 412e8be
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Showing 2 changed files with 63 additions and 85 deletions.
144 changes: 61 additions & 83 deletions index.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,41 +3,31 @@
// Expose.
module.exports = List

List.Item = ListItem

var ListPrototype = List.prototype
var ListItemPrototype = ListItem.prototype
var IterPrototype = Iter.prototype

/* istanbul ignore next */
var $iterator = typeof Symbol === 'undefined' ? undefined : Symbol.iterator

ListPrototype.tail = ListPrototype.head = null

List.Item = ListItem
List.of = of
List.from = from

ListPrototype.tail = ListPrototype.head = null
ListPrototype.toArray = toArray
ListPrototype.prepend = prepend
ListPrototype.append = append

/* istanbul ignore else */
if ($iterator !== undefined) {
ListPrototype[$iterator] = iterator
}
if ($iterator !== undefined) ListPrototype[$iterator] = iterator

ListItemPrototype.next = ListItemPrototype.prev = ListItemPrototype.list = null

ListItemPrototype.prepend = prependItem
ListItemPrototype.append = appendItem
ListItemPrototype.detach = detach

IterPrototype.next = next

// Constants.
var errorMessage =
'An argument without append, prepend, or detach methods was given to `List'

// Creates a new List: A linked list is a bit like an Array, but knows nothing
// about how many items are in it, and knows only about its first (`head`) and
// last (`tail`) items.
Expand All @@ -46,14 +36,13 @@ var errorMessage =
function List(/* items... */) {
this.size = 0

if (arguments.length > 0) {
if (arguments.length) {
appendAll(this, arguments)
}
}

// Creates a new list from the arguments (each a list item) passed in.
function appendAll(list, items) {
var length
var index
var item
var iter
Expand All @@ -71,10 +60,9 @@ function appendAll(list, items) {
list.append(item && item.value)
}
} else {
length = items.length
index = -1

while (++index < length) {
while (++index < items.length) {
list.append(items[index])
}
}
Expand Down Expand Up @@ -110,26 +98,24 @@ function toArray() {
// Prepends the given item to the list.
// `item` will be the new first item (`head`).
function prepend(item) {
var self = this
var head = self.head

if (!item) {
return false
}

if (!item.append || !item.prepend || !item.detach) {
throw new Error(errorMessage + '#prepend`.')
throw new Error(
'An argument without append, prepend, or detach methods was given to `List#prepend`.'
)
}

if (head) {
return head.prepend(item)
if (this.head) {
return this.head.prepend(item)
}

item.detach()

item.list = self
self.head = item
self.size++
item.list = this
this.head = item
this.size++

return item
}
Expand All @@ -143,32 +129,28 @@ function append(item) {
}

if (!item.append || !item.prepend || !item.detach) {
throw new Error(errorMessage + '#append`.')
throw new Error(
'An argument without append, prepend, or detach methods was given to `List#append`.'
)
}

var self = this
var head = self.head
var tail = self.tail

// If self has a last item, defer appending to the last items append method,
// and return the result.
if (tail) {
return tail.append(item)
if (this.tail) {
return this.tail.append(item)
}

// If self has a first item, defer appending to the first items append method,
// and return the result.
if (head) {
return head.append(item)
if (this.head) {
return this.head.append(item)
}

// …otherwise, there is no `tail` or `head` item yet.

item.detach()

item.list = self
self.head = item
self.size++
item.list = this
this.head = item
this.size++

return item
}
Expand All @@ -185,25 +167,22 @@ function ListItem() {}

// Detaches the item operated on from its parent list.
function detach() {
var self = this
var list = self.list
var previous = self.prev
var next = self.next
var list = this.list

if (!list) {
return self
return this
}

// If self is the last item in the parent list, link the lists last item to
// the previous item.
if (list.tail === self) {
list.tail = previous
if (list.tail === this) {
list.tail = this.prev
}

// If self is the first item in the parent list, link the lists first item to
// the next item.
if (list.head === self) {
list.head = next
if (list.head === this) {
list.head = this.next
}

// If both the last and first items in the parent list are the same, remove
Expand All @@ -213,34 +192,34 @@ function detach() {
}

// If a previous item exists, link its next item to selfs next item.
if (previous) {
previous.next = next
if (this.prev) {
this.prev.next = this.next
}

// If a next item exists, link its previous item to selfs previous item.
if (next) {
next.prev = previous
if (this.next) {
this.next.prev = this.prev
}

// Remove links from self to both the next and previous items, and to the
// parent list.
self.prev = self.next = self.list = null
this.prev = this.next = this.list = null

list.size--

return self
return this
}

// Prepends the given item *before* the item operated on.
function prependItem(item) {
var list = this.list

if (!item || !item.append || !item.prepend || !item.detach) {
throw new Error(errorMessage + 'Item#prepend`.')
throw new Error(
'An argument without append, prepend, or detach methods was given to `ListItem#prepend`.'
)
}

var self = this
var list = self.list
var previous = self.prev

// If self is detached, return false.
if (!list) {
return false
Expand All @@ -250,27 +229,27 @@ function prependItem(item) {
item.detach()

// If self has a previous item...
if (previous) {
item.prev = previous
previous.next = item
if (this.prev) {
item.prev = this.prev
this.prev.next = item
}

// Connect the prependee.
item.next = self
item.next = this
item.list = list

// Set the previous item of self to the prependee.
self.prev = item
this.prev = item

// If self is the first item in the parent list, link the lists first item to
// the prependee.
if (self === list.head) {
if (this === list.head) {
list.head = item
}

// If the the parent list has no last item, link the lists last item to self.
if (!list.tail) {
list.tail = self
list.tail = this
}

list.size++
Expand All @@ -280,14 +259,14 @@ function prependItem(item) {

// Appends the given item *after* the item operated on.
function appendItem(item) {
var list = this.list

if (!item || !item.append || !item.prepend || !item.detach) {
throw new Error(errorMessage + 'Item#append`.')
throw new Error(
'An argument without append, prepend, or detach methods was given to `ListItem#append`.'
)
}

var self = this
var list = self.list
var next = self.next

if (!list) {
return false
}
Expand All @@ -296,21 +275,21 @@ function appendItem(item) {
item.detach()

// If self has a next item…
if (next) {
item.next = next
next.prev = item
if (this.next) {
item.next = this.next
this.next.prev = item
}

// Connect the appendee.
item.prev = self
item.prev = this
item.list = list

// Set the next item of self to the appendee.
self.next = item
this.next = item

// If the the parent list has no last item or if self is the parent lists last
// item, link the lists last item to the appendee.
if (self === list.tail || !list.tail) {
if (this === list.tail || !list.tail) {
list.tail = item
}

Expand All @@ -326,9 +305,8 @@ function Iter(item) {

// Move the `Iter` to the next item.
function next() {
var current = this.item
this.value = current
this.done = !current
this.item = current ? current.next : undefined
this.value = this.item
this.done = !this.item
this.item = this.item ? this.item.next : undefined
return this
}
4 changes: 2 additions & 2 deletions package.json
View file
Original file line number Diff line number Diff line change
Expand Up @@ -57,8 +57,8 @@
"prettier": true,
"esnext": false,
"rules": {
"unicorn/prefer-spread": "off",
"no-multi-assign": "off"
"no-multi-assign": "off",
"unicorn/explicit-length-check": "off"
},
"ignores": [
"*.ts",
Expand Down

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