Class List<T>

GoJS® Diagramming Components
version 3.0.16
by Northwoods Software®

An ordered iterable collection. In TypeScript it is a generic class that enforces at compile-time the type of elements that may be added to the List.

An example usage:

  const list = new go.List();  // or in TypeScript: new go.List<go.Point>();
  list.add(new go.Point(0, 0));
  list.add(new go.Point(20, 10));
  list.add(new go.Point(10, 20));
  // now list.length === 3
  // and list.elt(1) instanceof go.Point

You can iterate over the items in a List:

  const it = aList.iterator;
  while (it.next()) {
    console.log("#" + it.key + " is " + it.value);
  }

Or:

  aList.each(val => {
    console.log(val);
  });

The key will range from zero to count-1.

For convenience this GoJS List class has synonyms for the following methods and property:

get(idx): elt
set(idx,val): setElt
has(val): has
delete(val): delete
clear(): clear
size: count

The constructor now takes an optional Iterable or Array argument that provides the initial elements for the new List.

Note that GoJS iteration is quite different than ECMAScript iteration, so that functionality has not been made somewhat compatible. These collection classes were defined in GoJS before the ECMAScript collection classes were proposed.

Type Parameters

Implements

Iterable<T>

Index

Constructors

constructor

new List<T>(coll?: T[] | Iterable<T>): List<T>
There are two possible constructors:

new go.List(), for JavaScript

new go.List<type>() for TypeScript, to enforce type checking.

Typical usage would be something like:
```
  const list = new go.List();  // keep a list of GraphObjects
```
Type Parameters
- T
Parameters
- Optional coll: T[] | Iterable<T>
  an optional collection of items to add.
Returns List<T>

Accessors

`Readonly`count
: number

This read-only property is the length of the List.

`Readonly`iterator
: Iterator<T>

Gets an object that you can use for iterating over the List. The key will be an integer from zero to the count-1. The value will be the item at that index in the list. Typical usage:
```
  const it = aList.iterator;
  while (it.next()) {
    . . . "index: " + it.key + " value: " + it.value . . .
  }
```

`Readonly`iteratorBackwards
: Iterator<T>

Gets an object that you can use for iterating over the List in backwards order. The key will be an integer from count-1 to zero. The value will be the item at that index in the list. The list is not modified by traversing in reverse order. Typical usage:
```
  const it = aList.iteratorBackwards;
  while (it.next()) {
    . . . 'key: ' + it.key + ' value: ' + it.value . . .
  }
```

`Readonly`length
: number

This read-only property is the length of the List, a synonym for the count property.

`Readonly`size
: number

This read-only property is the length of the List.

Methods

[iterator]

[iterator](): IterableIterator<T>
This class implements the JavaScript Symbol.iterator, and can be used with spread syntax or for ... of statements.

Returns IterableIterator<T>

add

add(val: T): List<T>
Adds a given value to the end of the List.

Be careful not to call this method while iterating over the collection.
Parameters
- val: T
Returns List<T>
This modified List.

addAll

addAll(coll: T[] | Iterable<T>): List<T>
Adds all of the values of a collection to the end of this List.

Be careful not to call this method while iterating over the collection.
Parameters
- coll: T[] | Iterable<T>
  the collection of items to add.
Returns List<T>
This modified List.

`Virtual`all

all(pred: ((a: T) => boolean)): boolean
This is true if all invocations of the given predicate on items in the collection are true.

Call the given predicate on each item in the collection. As soon as a call returns false, this returns false. Otherwise this returns true. For an empty collection this returns true.
Parameters
- pred: ((a: T) => boolean)
  This function must not have any side-effects.
  - - (a: T): boolean
    - Parameters
      a: T
      Returns boolean
Returns boolean
True if all predicate calls are true; false otherwise.

`Virtual`any

any(pred: ((a: T) => boolean)): boolean
This is true if any invocation of the given predicate on items in the collection is true.

Call the given predicate on each item in the collection. As soon as a call returns true, this returns true. Otherwise this returns false. For an empty collection this returns false.
Parameters
- pred: ((a: T) => boolean)
  This function must not have any side-effects.
  - - (a: T): boolean
    - Parameters
      a: T
      Returns boolean
Returns boolean
True if any predicate call is true; false otherwise.

clear

clear(): void
Clears the List. This sets the count to zero.

Be careful not to call this method while iterating over the collection.

Returns void

contains

contains(val: T): boolean
Returns whether the given value is in this List.
Parameters
- val: T
  The value to check.
Returns boolean
Whether or not the value is contained within the List.

`Virtual`copy

copy(): List<T>
Makes a shallow copy of this List. The values are not copied, so if they are objects they may continue to be shared with the original List.

Returns List<T>
The new List with the same elements.

delete

delete(val: T): boolean
Removes a given value (if found) from the List.

Be careful not to call this method while iterating over the collection.
Parameters
- val: T
  The value to remove.
Returns boolean
true if the value was found and removed, false otherwise.

`Virtual`each

each(func: ((a: T) => void)): List<T>
Call the given function on each item in the collection.
Parameters
- func: ((a: T) => void)
  This function must not modify the collection.
  - - (a: T): void
    - Parameters
      a: T
      Returns void
Returns List<T>
This List itself

elt

elt(i: number): T
Returns the element at the given index.
Parameters
- i: number
  int The index of the element to return.
Returns T
the value at the given index.

first

first(): T
Returns the first item in the list, or null if there is none.

Returns T
This returns null if there are no items in the list.

get

get(i: number): T
Returns the element at the given index.
Parameters
- i: number
  int The index of the element to return.
Returns T
the value at the given index.

has

has(val: T): boolean
Returns whether the given value is in this List.
Parameters
- val: T
  The value to check.
Returns boolean
Whether or not the value is contained within the List.

indexOf

indexOf(val: T): number
Returns the index of the given value if it is in this List.
Parameters
- val: T
  The value to check.
Returns number
returns -1 if the value is not in this list.

insertAt

insertAt(i: number, val: T): void
Insert a value before the index i.

Be careful not to call this method while iterating over the collection.
Parameters
- i: number
  int The index to insert before.
- val: T
  The value to insert.
Returns void

last

last(): T
Returns the last item in the list, or null if these is none.

Returns T
This returns null if there are no items in the list.

pop

pop(): T
Returns the last item in the list and removes it from the list, or just return null if these is none. Use add to push an item onto the end of the list. Use last to get the last item without reducing the length of the list.

Returns T
This returns null if there are no items in the list.

push

push(val: T): void
Adds a given value to the end of the List.

Be careful not to call this method while iterating over the collection.
Parameters
- val: T
Returns void

remove

remove(val: T): boolean
Removes a given value (if found) from the List.

Be careful not to call this method while iterating over the collection.
Parameters
- val: T
  The value to remove.
Returns boolean
true if the value was found and removed, false otherwise.

removeAt

removeAt(i: number): void
Removes a value at a given index from the List.

Be careful not to call this method while iterating over the collection.
Parameters
- i: number
  int The index to remove.
Returns void

removeRange

removeRange(from: number, to: number): List<T>
Removes a range of values from the List, given both the starting and the ending zero-based indexes. For example,
```
list.removeRange(2, 4)
```
will remove elements 2, 3, and 4 from the list. If there were two or fewer elements in the list to begin with, the list is unchanged. If from is greater than to, the list is unchanged. If from is greater than or equal to the length, the list is unchanged. If to is less than zero, the list is unchanged.

Be careful not to call this method while iterating over the collection.
Parameters
- from: number
  int The starting index of the range to remove, inclusive; negative values are treated as zero
- to: number
  int The ending index of the range to remove, inclusive; values greater than the length of the list are treated as referring to the last element
Returns List<T>
This modified List

reverse

reverse(): List<T>
Reverse the order of items in this List.

Returns List<T>
This modified List.

set

set(i: number, val: T): void
Set the element at the given index to a given value.
Parameters
- i: number
  int The index of the element to set.
- val: T
  The value to set at the index.
Returns void

setElt

setElt(i: number, val: T): void
Set the element at the given index to a given value.
Parameters
- i: number
  int The index of the element to set.
- val: T
  The value to set at the index.
Returns void

sort

sort(sortfunc: ((a: T, b: T) => number)): List<T>
Sort the List according to a comparison function.
Parameters
- sortfunc: ((a: T, b: T) => number)
  This function is passed two items in the list. It should return zero if they are equal, less than zero if the first value should come before the second value, or greater than zero if the first value should come after the second value.
  - - (a: T, b: T): number
    - Parameters
      a: T
      b: T
      Returns number
Returns List<T>
This modified List.

toArray

toArray(): T[]
Produces a JavaScript Array from the contents of this List.

Returns T[]
A copy of the List in Array form.

toSet

toSet(): Set<T>
Converts the List to a go.Set. The count of the resulting Set may be less than the count of this List if any duplicates were removed.

Returns Set<T>
A copy of the contents of this List, but with duplicates removed and ordering lost.

Class List<T>

Type Parameters

Implements

Index

Constructors

Accessors

Methods

Constructors

constructor

Type Parameters

Parameters

Optional coll: T[] | Iterable<T>

Returns List<T>

Accessors

Readonlycount: number

Readonlyiterator: Iterator<T>

ReadonlyiteratorBackwards: Iterator<T>

Readonlylength: number

Readonlysize: number

Methods

[iterator]

Returns IterableIterator<T>

add

Parameters

val: T

Returns List<T>

addAll

Parameters

coll: T[] | Iterable<T>

Returns List<T>

Virtualall

Parameters

pred: ((a: T) => boolean)

Parameters

a: T

Returns boolean

Returns boolean

Virtualany

Parameters

pred: ((a: T) => boolean)

Parameters

a: T

Returns boolean

Returns boolean

clear

Returns void

contains

Parameters

val: T

Returns boolean

Virtualcopy

Returns List<T>

delete

Parameters

val: T

Returns boolean

Virtualeach

Parameters

func: ((a: T) => void)

Parameters

a: T

Returns void

Returns List<T>

elt

Parameters

i: number

Returns T

first

Returns T

get

Parameters

i: number

Returns T

has

Parameters

val: T

Returns boolean

indexOf

Parameters

val: T

`Optional` coll: T[] | Iterable<T>

`Readonly`count
: number

`Readonly`iterator
: Iterator<T>

`Readonly`iteratorBackwards
: Iterator<T>

`Readonly`length
: number

`Readonly`size
: number

`Virtual`all

`Virtual`any

`Virtual`copy

`Virtual`each