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Array

ECMAScript Array prototype object.

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Inherits :

Properties

ECMAScript
Numberlength

Static Methods

ECMAScript
BooleanisArray ( Object obj )

Constructors

ECMAScript
Array ()
Array ( Object firstElement, … )
Array ( Number len )

Methods

ECMAScript
Arrayconcat ( Object element1, … )
Booleanevery ( Function callbackfn, Object thisArg=undefined )
Arrayfilter ( Function callbackfn, Object thisArg=undefined )
voidforEach ( Function callbackfn, Object thisArg=undefined )
NumberindexOf ( Object searchElement, Number fromIndex=0 )
Stringjoin ( String separator=“,” )
NumberlastIndexOf ( Object searchElement, Number fromIndex=length-1 )
Arraymap ( Function callbackfn, Object thisArg=undefined )
Objectpop ()
Numberpush ( Object element1, … )
Objectreduce ( Function callbackfn, Object initialValue=undefined )
ObjectreduceRight ( Function callbackfn, Object initialValue=undefined )
Arrayreverse ()
Objectshift ()
Arrayslice ( Number startIndex, Number endIndex=length )
Booleansome ( Function callbackfn, Object thisArg=undefined )
Arraysort ( Function comparisonFunction )
Arraysplice ( Number startIndex, Number deleteCount, … )
StringtoLocaleString ()
StringtoString ()
Numberunshift ( Object element1, … )
DAZ Script
Numberfind ( Object element )
NumberpushIfNotExists ( Object element1, … )

Detailed Description

An array is a data type that allows you to work with a list of elements. These elements can be any QObject derived object. Multi-dimensional arrays are achieved by using array elements that are arrays themselves.

Array Creation

Arrays can be constructed using array literals, or by using the new operator. They can be extended dynamically by simply creating elements at non-existent index positions.

Example:

Array literal

var aTemp = [];

Example:

Array literal

var aTemp = [ "a", "b", "c", "d" ];

Example:

Using the new operator, initialized with a size, but with undefined elements

var aTemp = new Array( 4 );

Example:

Using the new operator, defining all elements

var aTemp = new Array( "a", "b", "c", "d" );

Example:

Multi-Dimensional, dynamically extended

var aTemp = [ "a", "b", "c", "d" ];
var aTemp2 = [];
 
for ( var i = 0; i < aTemp.length; i++ ) {
	aTemp2[ i ] = new Array( 2 );
	aTemp2[ i ][ 0 ] = i;
	aTemp2[ i ][ 1 ] = aTemp[ i ];
}
// aTemp2 == [ [ 0, "a" ], [ 1, "b" ], [ 2, "c" ], [ 3, "d" ] ]

Array Access

Array elements are accessed by their names. Names can be integers or strings. As integers, element names are zero-based, meaning the first element is at 0, the second element is at 1 and so on. As strings, elements can act as normal properties, and can be accessed by using the square bracket operator ([]) or by directly dereferencing the Array object and specifying the property name (.name). These two accessor types can be mixed freely.

Example:

Integer access

var aTemp = [ "a", "b", "c", "d" ];
var sTemp = aTemp[ 2 ];
// sTemp == "c";

Example:

Multi-Dimensional, integer access

var aTemp = [ [ "a", 5 ], [ "b", 10 ], [ "c", 15 ], [ "d", 20 ] ];
var nTemp = aTemp[ 2 ][ 1 ];
// nTemp == 15;

Example:

String access, using the square bracket operator

var aTemp = [];
 
// Assignment:
aTemp[ "one" ] = "a";
aTemp[ "two" ] = "b";
 
// Retrieval:
var sTemp = aTemp[ "one" ];
// sTemp == "a"
var sTemp2 = aTemp[ "two" ];
// sTemp2 == "b"

Example:

String access, dereferencing the Array, specifying properties

var aTemp = [];
 
// Assignment:
aTemp.one = "a";
aTemp.two = "b";
 
// Retrieval:
var sTemp = aTemp.one;
// sTemp == "a"
var sTemp2 = aTemp.two;
// sTemp2 == "b"

Array Iteration

An array can be iterated over by using a for or for...in loop.

Example:

Iteration of element names as integers, using the for control statement

var aTemp = [ "a", "b", "c", "d" ];
var sTemp = "";
 
for( var i = 0; i < aTemp.length; i++ ){
	sTemp += aTemp[ i ];
}
// sTemp == "abcd"

Example:

Iteration of element names as strings, using the for...in control statement

var aTemp = [];
aTemp[ "first" ] = "a";
aTemp[ "second" ] = "b";
aTemp[ "third" ] = "c";
aTemp[ "fourth" ] = "d";
// element names are sorted alphanumerically
// aTemp == [ "first" : "a", "fourth" : "d", "second" : "b", "third" : "c" ]
 
var sTemp = "";
 
for( var sElement in aTemp ){
	sTemp += aTemp[ sElement ];
}
// sTemp == "adbc"

Todo

Investigate whether there is a [Qt] bug in the return value of reverse, sort and slice; reference vs. copy.

Properties


Number : length

Holds the number of elements in the array. (Read Only)

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp.length ); //4

Static Methods


Boolean : isArray( Object obj )

Return Value:

  • true if obj is an array, otherwise false.

Example:

var aTemp = [];
print( Array.isArray( aTemp ) ); //true
 
var oTmp = {};
print( Array.isArray( oTmp ) ); //false

Constructors


Array()

Default Constructor.

Example:

var aTemp = new Array();
print( aTemp.length ); //0

Array( Object firstElement, … )

Constructs an array with one or more elements.

Parameter(s):

  • firstElement - The first element to add to the array.
  • - Optional additional elements to add to the array.

Example:

var aTemp = new Array( "a", "b", "c", "d" );
print( aTemp.length ); //4

Array( Number len )

Constructs an array of the given length. The arrays elements will be uninitialized (undefined).

Parameter(s):

  • len - The number of items in the new array.

Example:

var aTemp = new Array( 10 );
print( aTemp.length ); //10

Methods


Array : concat( Object element1, … )

Parameter(s):

  • element1 - The first element to concatenate with the array.
  • - Additional elements to concatenate with the array. (Optional)

Return Value:

  • A new array consisting of the concatenated contents.

Example:

var aTemp = [ "a", "b", "c" ];
print( aTemp ); //a,b,c
 
var nTemp = 5;
print( aTemp.concat( nTemp ) ); //a,b,c,5
var aTemp = [ "a", "b", "c" ];
print( aTemp ); //a,b,c
 
var aTemp2 = [ 1, 2, 3 ];
print( aTemp2 ); //1,2,3
 
print( aTemp.concat( aTemp2 ) ); //a,b,c,1,2,3

Boolean : every( Function callbackfn, Object thisArg=undefined )

Invokes a function for each non-empty element in the array, in ascending order, until or unless that function returns false.

Parameter(s):

  • callbackfn - A function that accepts 3 arguments and returns true or false; the arguments are the value of the element, the index of the element and the object being traversed
  • thisArg - An optional argument that defines the this value for each invocation of callbackfn.

Return Value:

  • true if callbackfn returns true for every element in the array, otherwise false.

Example:

function greaterThan5( nValue, nIndex, aValues ) {
	return nValue > 5;
}
 
function greaterThan10( nValue, nIndex, aValues ) {
	return nValue > 10;
}
 
var aTmp = [10, 20, 30, 40, 50];
print( aTmp.every( greaterThan5 ) ); //true
print( aTmp.every( greaterThan10 ) ); //false

Array : filter( Function callbackfn, Object thisArg=undefined )

Invokes a function for each non-empty element in the array.

Parameter(s):

  • callbackfn - A function that accepts 3 arguments and returns true or false; the arguments are the value of the element, the index of the element and the object being traversed
  • thisArg - An optional argument that defines the this value for each invocation of callbackfn.

Return Value:

  • A new array of all the elements for which callbackfn returns true.

Example:

function evenNumber( nValue, nIndex, aValues ) {
	var nRemainder = nValue % 2;
	return nRemainder == 0;
}
 
function oddNumber( nValue, nIndex, aValues ) {
	var nRemainder = nValue % 2;
	return nRemainder == 1;
}
 
var aTemp = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
print( aTemp.filter( evenNumber ) ); //2,4,6,8,10
print( aTemp.filter( oddNumber ) ); //1,3,5,7,9

void : forEach( Function callbackfn, Object thisArg=undefined )

Invokes a function for each non-empty element in the array.

Parameter(s):

  • callbackfn - A function that accepts 3 arguments; the value of the element, the index of the element and the object being traversed.
  • thisArg - An optional argument that defines the this value for each invocation of callbackfn.

Example:

function printValue( nValue, nIndex, aValues ) {
	print( nIndex, nValue, aValues[ nIndex ] );
}
 
var aTemp = [10, 20, 30, 40, 50];
aTemp.forEach( printValue );
//0 10 10
//1 20 20
//2 30 30
//3 40 40
//4 50 50

Number : indexOf( Object searchElement, Number fromIndex=0 )

Compares searchElement to the elements of the array, in ascending order, using Strict Equals.

Parameter(s):

  • searchElement - The Object to search for.
  • fromIndex - An optional offset position within the array to begin searching from.

Return Value:

  • The index of the position of searchElement in the array, or -1 if searchElement is not found.

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp.indexOf( "c" ) ); //2

String : join( String separator=“,” )

Parameter(s):

  • separator - The character used to separate the elements in the list.

Return Value:

  • A string containing all elements in the array, with the given separator between each.

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp.join( ":" ) ); //a:b:c:d

See Also:

  • toString()

Number : lastIndexOf( Object searchElement, Number fromIndex=length-1 )

Compares searchElement to the elements of the array, in descending order, using strict equality.

Parameter(s):

  • searchElement - The Object to search for.
  • fromIndex - An optional offset position within the array to begin searching from.

Return Value:

  • The index of the position of searchElement in the array, or -1 if searchElement is not found.

Example:

var aTemp = [ "a", "b", "c", "d", "a", "b", "c", "d" ];
print( aTemp.lastIndexOf( "c" ) ); //6

Array : map( Function callbackfn, Object thisArg=undefined )

Invokes a function for each non-empty element in the array.

Parameter(s):

  • callbackfn - A function that accepts 3 arguments; the arguments are the value of the element, the index of the element and the object being traversed.
  • thisArg - An optional argument that defines the this value for each invocation of callbackfn.

Return Value:

  • A new array consisting of the results of calling callbackfn for each non-empty element in the array.

Example:

function addDoe( sValue, nIndex, aValues ) {
	return sValue + " Doe";
}
 
var aTemp = ["John", "Jane", "Baby"];
print( aTemp.map( addDoe ) ); //John Doe,Jane Doe,Baby Doe

Object : pop()

Removes the last (right-most) element from the array.

Return Value:

  • The removed element.

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp ); //a,b,c,d
 
print( aTemp.pop() ); //d
print( aTemp ); //a,b,c

Number : push( Object element1, … )

Appends one or more elements onto the end (right) of the array.

Parameter(s):

  • element1 - The element to append.
  • - Optional additional elements to append.

Return Value:

  • The new length of the array.

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp ); //a,b,c,d
print( aTemp.push( "e" ) ); //a,b,c,d,e

Object : reduce( Function callbackfn, Object initialValue=undefined )

Invokes a function for each element in the array, in ascending order.

Parameter(s):

  • callbackfn - A function that accepts 4 arguments; the previousValue (or value from the previous call to callbackfn), the currentValue (value of the current element), the currentIndex and the object being traversed.
  • initialValue - An optional argument that defines the previousValue for initial invocation of callbackfn; if not defined previousValue will be the first element in the array and currentValue will be the second element.

Return Value:

  • A new Object consisting of the result of calling callbackfn for each element in the array.

Example:

function accumulate( nPreviousValue, nValue, nIndex, aValues ) {
	return nPreviousValue + nValue;
}
 
var aTemp = [10, 20, 30, 40, 50];
print( aTemp.reduce( accumulate, 5 ) ); //155

Object : reduceRight( Function callbackfn, Object initialValue=undefined )

Invokes a function for each element in the array, in descending order.

Parameter(s):

  • callbackfn - A function that accepts 4 arguments; the previousValue (or value from the previous call to callbackfn), the currentValue (value of the current element), the currentIndex and the object being traversed.
  • initialValue - An optional argument that defines the previousValue for initial invocation of callbackfn; if not defined previousValue will be the first element in the array and currentValue will be the second element.

Return Value:

  • A new Object consisting of the result of calling callbackfn for each element in the array.

Example:

function accumulate( nPreviousValue, nValue, nIndex, aValues ) {
	return nPreviousValue - nValue;
}
 
var aTemp = [10, 20, 30, 40, 50];
print( aTemp.reduceRight( accumulate, 155 ) ); //5

Array : reverse()

Reverses the order of the elements in the array.

Return Value:

  • A reference to the array.

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp.reverse() ); //d,c,b,a
var aTemp = [ "a", "b", "c", "d" ];
print( aTemp ); //a,b,c,d
print( aTemp.reverse() ); //d,c,b,a

Object : shift()

Removes the first (left-most) element in the array.

Return Value:

  • The removed element.

Example:

var aTemp = [ "a", "b", "c", "d" ];
print( aTemp ); //a,b,c,d
 
var sTemp = aTemp.shift();
print( sTemp ); //a
print( aTemp ); //b,c,d

Array : slice( Number startIndex, Number endIndex=length )

Parameter(s):

  • startIndex - The index of the first element in the slice. If negative, the value is treated as length + startIndex, where length is the length of the array.
  • endIndex - The index of the element to end the slice at. Defaults to the length of the array. If negative, the value is treated as length + endIndex, where length is the length of the array. (Optional)

Return Value:

  • A copy of the array from the element at startIndex to (but not including) the element at endIndex.

Example:

var aTemp = [ "a", "b", "c", "d", "e", "f" ];
var aTemp2 = aTemp.slice( 2 );
print( aTemp ); //a,b,c,d,e,f
print( aTemp2 ); //c,d,e,f
var aTemp = [ "a", "b", "c", "d", "e", "f" ];
var aTemp2 = aTemp.slice( 1, 4 );
print( aTemp ); //a,b,c,d,e,f
print( aTemp2 ); //b,c,d

Boolean : some( Function callbackfn, Object thisArg=undefined )

Invokes a function for each non-empty element in the array, in ascending order.

Parameter(s):

  • callbackfn - A function that accepts 3 arguments and returns true or false; the arguments are the value of the element, the index of the element and the object being traversed.
  • thisArg - An optional argument that defines the this value for each invocation of callbackfn.

Return Value:

  • true if callbackfn returns true for any element in the array, otherwise false.

Array : sort( Function comparisonFunction )

Sorts the array using comparisonFunction. If no Function is provided, default sorting is applied.

Parameter(s):

  • comparisonFunction - An optional function to call to compare items in the array.

Return Value:

  • A reference to the array.

Example:

No arguments

var aTemp = new [ "a", "c", "d", "b" ];
aTemp.sort();
// aTemp == [ "a", "b", "c", "d" ]

Example:

Comparison function

// -1 if a < b, 0 if a == b, 1 if a > b
function numerically( a, b ){
	return a < b ? -1 : a > b ? 1 : 0;
}
 
var aTemp = [ 8, 90, 1, 4, 843, 221 ];
aTemp.sort( numerically );
// aTemp == [ 1, 4, 8, 90, 221, 843 ]

Array : splice( Number startIndex, Number deleteCount, … )

Splices elements into the array.

Parameter(s):

  • startIndex - The index in the array to place the new element(s).
  • deleteCount - The number of elements in the array to delete.
  • - Optional element(s) to insert into the array.

Return Value:

  • An array containing the deleted elements (if any).

Example:

Insert

var aTemp = [ "a", "b", "c", "d" ];
aTemp.splice( 2, 0, "X" );
print( aTemp ); //a,b,X,c,d
var aTemp = [ "a", "b", "c", "d" ];
aTemp.splice( 2, 0, "X", "Y" );
print( aTemp ); //a,b,X,Y,c,d

Example:

Remove

var aTemp = [ "a", "b", "c", "d" ];
var aTemp2 = aTemp.splice( 2, 1 );
print( aTemp ); //a,b,d
print( aTemp2 ); //c

Example:

Replace

var aTemp = [ "a", "b", "c", "d" ];
var aTemp2 = aTemp.splice( 2, 1, "X" );
print( aTemp ); //a,b,X,d
print( aTemp2 ); //c
var aTemp = [ "a", "b", "c", "d" ];
var aTemp2 = aTemp.splice( 2, 1, "X", "Y" );
print( aTemp ); //a,b,X,Y,d
print( aTemp2 ); //c

String : toLocaleString()

Provides a locale-aware version of toString().

Return Value:

  • A string containing all elements of an array together, separated by a locale-specific separator.

See Also:

  • toString(), join()

String : toString()

Return Value:

  • A string containing all elements of an array together, separated by commas. This method is used when the array is used in the context of string concatenation or is used as a text value (e.g. for printing).

Example:

var aTemp = [ "a", "b", "c", "d" ];
var sTemp = aTemp.toString();
// sTemp == "a,b,c,d"

See Also:

  • join()

Number : unshift( Object element1, … )

Inserts the element(s) at the beginning (left) of the array.

Parameter(s):

  • element1 - The first element to insert into the array.
  • - Optional additional element(s) to insert into the array.

Return Value:

  • The number of objects in the array.

Example:

var aTemp = [ "a", "b", "c", "d" ];
var nTemp = aTemp.unshift( "X" );
print( aTemp ); //X,a,b,c,d
print( nTemp ); //5
var aTemp = [ "a", "b", "c", "d" ];
var nTemp = aTemp.unshift( "X", "Y" );
print( aTemp ); //X,Y,a,b,c,d
print( nTemp ); //6

Number : find( Object element )

Parameter(s):

  • element - The item to search for in the array.

Return Value:

  • The index of element, if found. -1 if element is not found.

Example:

var aTemp = [ "a", "b", "c", "d", "e" ];
print( aTemp.find( "d" ) ); //3

Number : pushIfNotExists( Object element1, … )

Pushes one or more elements onto the end (right) of the array, if it doesn't already exist in the array.

Parameter(s):

  • element1 - The first element to append to the array.
  • - Optional additional element(s) to insert into the array.

Return Value:

  • The new length of the array.

Example:

var aTemp = [ "a", "b", "c", "d" ];
aTemp.pushIfNotExists( "e" );
// aTemp == [ "a", "b", "c", "d", "e" ]