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Lets you work with arrays.
The Array object constructor:
new Array(arrayLength)
new Array(element0, element1, ..., elementN)
An array literal:
[element0, element1, ..., elementN]
JavaScript 1.2 when you specify LANGUAGE="JavaScript1.2" in the <SCRIPT> tag:
new Array(element0, element1, ..., elementN)
An array is an ordered set of values associated with a single variable name.
The following example creates an Array object with an array literal; the coffees array contains three elements and a length of three:
coffees = ["French Roast", "Columbian", "Kona"]
You can construct a dense array of two or more elements starting with index 0 if you define initial values for all elements. A dense array is one in which each element has a value. The following code creates a dense array with three elements:
myArray = new Array("Hello", myVar, 3.14159)
Indexing an array.
You index an array by its ordinal number. For example, assume you define the following array:
myArray = new Array("Wind","Rain","Fire")
You then refer to the first element of the array as myArray[0] and the second element of the array as myArray[1].
Specifying a single parameter.
When you specify a single numeric parameter with the Array constructor, you specify the initial length of the array. The following code creates an array of five elements:
billingMethod = new Array(5)
The behavior of the Array constructor depends on whether the single parameter is a number.
The following code creates an array of length 25, then assigns values to the first three elements:
musicTypes = new Array(25)
musicTypes[0] = "R&B"
musicTypes[1] = "Blues"
musicTypes[2] = "Jazz"
When you specify a single parameter with the Array constructor in JavaScript 1.2, the behavior depends on whether you specify LANGUAGE="JavaScript1.2" in the <SCRIPT> tag:
Increasing the array length indirectly.
An array's length increases if you assign a value to an element higher than the current length of the array. The following code creates an array of length 0, then assigns a value to element 99. This changes the length of the array to 100.
colors = new Array()
colors[99] = "midnightblue"
Creating an array using the result of a match.
The result of a match between a regular expression and a string can create an array. This array has properties and elements that provide information about the match. An array is the return value of RegExp.exec, String.match, and String.replace. To help explain these properties and elements, look at the following example and then refer to the table below:
<SCRIPT LANGUAGE="JavaScript1.2">
//Match one d followed by one or more b's followed by one d
//Remember matched b's and the following d
//Ignore case
myRe=/d(b+)(d)/i;
myArray = myRe.exec("cdbBdbsbz");
</SCRIPT>
The properties and elements returned from this match are as follows:
JavaScript 1.1 and earlier.
When you specify a single parameter with the Array constructor, you specify the initial length of the array. The following code creates an array of five elements:
billingMethod = new Array(5)
JavaScript 1.0.
You must index an array by its ordinal number; for example myArray[0].
In addition, this object inherits the watch and unwatch methods from Object.
Example 1. The following example creates an array, msgArray, with a length of 0, then assigns values to msgArray[0] and msgArray[99], changing the length of the array to 100.
msgArray = new Array()
msgArray[0] = "Hello"
msgArray[99] = "world"
// The following statement is true,
// because defined msgArray[99] element.
if (msgArray.length == 100)
myVar="The length is 100."
Example 2: Two-dimensional array. The following code creates a two-dimensional array and assigns the results to myVar.
myVar="Multidimensional array test; "
a = new Array(4)
for (i=0; i < 4; i++) {
a[i] = new Array(4)
for (j=0; j < 4; j++) {
a[i][j] = "["+i+","+j+"]"
}
}
for (i=0; i < 4; i++) {
str = "Row "+i+":"
for (j=0; j < 4; j++) {
str += a[i][j]
}
myVar += str +"; "
}
This example assigns the following string to myVar (line breaks are used here for readability):
Multidimensional array test;
Row 0:[0,0][0,1][0,2][0,3];
Row 1:[1,0][1,1][1,2][1,3];
Row 2:[2,0][2,1][2,2][2,3];
Row 3:[3,0][3,1][3,2][3,3];
Joins two arrays and returns a new array.
concat(arrayName2, arrayName3, ..., arrayNameN)
concat does not alter the original arrays, but returns a "one level deep" copy that contains copies of the same elements combined from the original arrays. Elements of the original arrays are copied into the new array as follows:
If a new element is added to either array, the other array is not affected.
The following code concatenates two arrays:
alpha=new Array("a","b","c")
numeric=new Array(1,2,3)
alphaNumeric=alpha.concat(numeric) // creates array ["a","b","c",1,2,3]
The following code concatenates three arrays:
num1=[1,2,3]
num2=[4,5,6]
num3=[7,8,9]
nums=num1.concat(num2,num3) // creates array [1,2,3,4,5,6,7,8,9]
Specifies the function that creates an object's prototype. Note that the value of this property is a reference to the function itself, not a string containing the function's name.
See Object.constructor.
For an array created by a regular expression match, the zero-based index of the match in the string.
For an array created by a regular expression match, reflects the original string against which the regular expression was matched.
Joins all elements of an array into a string.
join(separator)
The string conversions of all array elements are joined into one string.
The following example creates an array, a, with three elements, then joins the array three times: using the default separator, then a comma and a space, and then a plus.
a = new Array("Wind","Rain","Fire")
myVar1=a.join() // assigns "Wind,Rain,Fire" to myVar1
myVar2=a.join(", ") // assigns "Wind, Rain, Fire" to myVar1
myVar3=a.join(" + ") // assigns "Wind + Rain + Fire" to myVar1
Array.reverse
An integer that specifies the number of elements in an array.
You can set the length property to truncate an array at any time. When you extend an array by changing its length property, the number of actual elements does not increase; for example, if you set length to 3 when it is currently 2, the array still contains only 2 elements.
In the following example, the getChoice function uses the length property to iterate over every element in the musicType array. musicType is a select element on the musicForm form.
function getChoice() {
for (var i = 0; i < document.musicForm.musicType.length; i++) {
if (document.musicForm.musicType.options[i].selected == true) {
return document.musicForm.musicType.options[i].text
}
}
}
The following example shortens the array statesUS to a length of 50 if the current length is greater than 50.
if (statesUS.length > 50) {
statesUS.length=50
}
Removes the last element from an array and returns that element. This method changes the length of the array.
pop()
None.
The following code creates the myFish array containing four elements, then removes its last element.
myFish = ["angel", "clown", "mandarin", "surgeon"];
popped = myFish.pop();
push, shift, unshift
Represents the prototype for this class. You can use the prototype to add properties or methods to all instances of a class. For information on prototypes, see Function.prototype.
Adds one or more elements to the end of an array and returns the last element added to the array. This method changes the length of the array.
push(element1, ..., elementN)
The behavior of the push method is analogous to the push function in Perl 4. Note that this behavior is different in Perl 5.
The following code creates the myFish array containing two elements, then adds two elements to it. After the code executes, pushed contains "lion".
myFish = ["angel", "clown"];
pushed = myFish.push("drum", "lion");
pop, shift, unshift
Transposes the elements of an array: the first array element becomes the last and the last becomes the first.
reverse()
None
The reverse method transposes the elements of the calling array object.
The following example creates an array myArray, containing three elements, then reverses the array.
myArray = new Array("one", "two", "three")
myArray.reverse()
This code changes myArray so that:
Array.join, Array.sort
Removes the first element from an array and returns that element. This method changes the length of the array.
shift()
None.
The following code displays the myFish array before and after removing its first element. It also displays the removed element:
myFish = ["angel", "clown", "mandarin", "surgeon"];
document.writeln("myFish before: " + myFish);
shifted = myFish.shift();
document.writeln("myFish after: " + myFish);
document.writeln("Removed this element: " + shifted);
This example displays the following:
myFish before: ["angel", "clown", "mandarin", "surgeon"]
myFish after: ["clown", "mandarin", "surgeon"]
Removed this element: angel
pop, push, unshift
Extracts a section of an array and returns a new array.
slice(begin[,end])
slice does not alter the original array, but returns a new "one level deep" copy that contains copies of the elements sliced from the original array. Elements of the original array are copied into the new array as follows:
If a new element is added to either array, the other array is not affected.
In the following example, slice creates a new array, newCar, from myCar. Both include a reference to the object myHonda. When the color of myHonda is changed to purple, both arrays reflect the change.
<SCRIPT LANGUAGE="JavaScript1.2">
//Using slice, create newCar from myCar.
myHonda = {color:"red",wheels:4,engine:{cylinders:4,size:2.2}}
myCar = [myHonda, 2, "cherry condition", "purchased 1997"]
newCar = myCar.slice(0,2)
//Write the values of myCar, newCar, and the color of myHonda
// referenced from both arrays.
document.write("myCar = " + myCar + "<BR>")
document.write("newCar = " + newCar + "<BR>")
document.write("myCar[0].color = " + myCar[0].color + "<BR>")
document.write("newCar[0].color = " + newCar[0].color + "<BR><BR>")
//Change the color of myHonda.
myHonda.color = "purple"
document.write("The new color of my Honda is " + myHonda.color + "<BR><BR>")
//Write the color of myHonda referenced from both arrays.
document.write("myCar[0].color = " + myCar[0].color + "<BR>")
document.write("newCar[0].color = " + newCar[0].color + "<BR>")
</SCRIPT>
This script writes:
myCar = [{color:"red", wheels:4, engine:{cylinders:4, size:2.2}}, 2,
"cherry condition", "purchased 1997"]
newCar = [{color:"red", wheels:4, engine:{cylinders:4, size:2.2}}, 2]
myCar[0].color = red newCar[0].color = red
The new color of my Honda is purple
myCar[0].color = purple
newCar[0].color = purple
Sorts the elements of an array.
sort(compareFunction)
If compareFunction is not supplied, elements are sorted by converting them to strings and comparing strings in lexicographic ("dictionary" or "telephone book," not numerical) order. For example, "80" comes before "9" in lexicographic order, but in a numeric sort 9 comes before 80.
If compareFunction is supplied, the array elements are sorted according to the return value of the compare function. If a and b are two elements being compared, then:
So, the compare function has the following form:
function compare(a, b) {
if (a is less than b by some ordering criterion)
return -1
if (a is greater than b by the ordering criterion)
return 1
// a must be equal to b
return 0
}
To compare numbers instead of strings, the compare function can simply subtract b from a:
function compareNumbers(a, b) {
return a - b
}
JavaScript uses a stable sort: the index partial order of a and b does not change if a and b are equal. If a's index was less than b's before sorting, it will be after sorting, no matter how a and b move due to sorting.
The behavior of the sort method changed between JavaScript 1.1 and
JavaScript 1.2.
In JavaScript 1.1, on some platforms, the sort method does not work. This method works on all platforms for JavaScript 1.2.
In JavaScript 1.2, this method no longer converts undefined elements to null; instead it sorts them to the high end of the array. For example, assume you have this script:
<SCRIPT>
a = new Array();
a[0] = "Ant";
a[5] = "Zebra";
function writeArray(x) {
for (i = 0; i < x.length; i++) {
document.write(x[i]);
if (i < x.length-1) document.write(", ");
}
}writeArray(a);
a.sort();
document.write("<BR><BR>");
writeArray(a);
</SCRIPT>
In JavaScript 1.1, JavaScript prints:
ant, null, null, null, null, zebra
ant, null, null, null, null, zebra
In JavaScript 1.2, JavaScript prints:
ant, undefined, undefined, undefined, undefined, zebra
ant, zebra, undefined, undefined, undefined, undefined
The following example creates four arrays and displays the original array, then the sorted arrays. The numeric arrays are sorted without, then with, a compare function.
<SCRIPT>
stringArray = new Array("Blue","Humpback","Beluga")
numericStringArray = new Array("80","9","700")
numberArray = new Array(40,1,5,200)
mixedNumericArray = new Array("80","9","700",40,1,5,200)
function compareNumbers(a, b) {
return a - b
}document.write("<B>stringArray:</B> " + stringArray.join() +"<BR>")
document.write("<B>Sorted:</B> " + stringArray.sort() +"<P>")document.write("<B>numberArray:</B> " + numberArray.join() +"<BR>")
document.write("<B>Sorted without a compare function:</B> " + numberArray.sort() +"<BR>")
document.write("<B>Sorted with compareNumbers:</B> " + numberArray.sort(compareNumbers) +"<P>")document.write("<B>numericStringArray:</B> " + numericStringArray.join() +"<BR>")
document.write("<B>Sorted without a compare function:</B> " + numericStringArray.sort() +"<BR>")
document.write("<B>Sorted with compareNumbers:</B> " + numericStringArray.sort(compareNumbers) +"<P>")document.write("<B>mixedNumericArray:</B> " + mixedNumericArray.join() +"<BR>")
document.write("<B>Sorted without a compare function:</B> " + mixedNumericArray.sort() +"<BR>")
document.write("<B>Sorted with compareNumbers:</B> " + mixedNumericArray.sort(compareNumbers) +"<BR>")
</SCRIPT>
This example produces the following output. As the output shows, when a compare function is used, numbers sort correctly whether they are numbers or numeric strings.
stringArray: Blue,Humpback,Beluga
Sorted: Beluga,Blue,Humpback
numberArray: 40,1,5,200
Sorted without a compare function: 1,200,40,5
Sorted with compareNumbers: 1,5,40,200
numericStringArray: 80,9,700
Sorted without a compare function: 700,80,9
Sorted with compareNumbers: 9,80,700
mixedNumericArray: 80,9,700,40,1,5,200
Sorted without a compare function: 1,200,40,5,700,80,9
Sorted with compareNumbers: 1,5,9,40,80,200,700
Array.join, Array.reverse
Changes the content of an array, adding new elements while removing old elements.
splice(index, howMany, [element1][, ..., elementN])
If you specify a different number of elements to insert than the number you're removing, the array will have a different length at the end of the call.
The splice method returns the element removed, if only one element is removed (howMany parameter is 1); otherwise, splice returns an array containing the removed elements.
The following script illustrate the use of splice:
<SCRIPT LANGUAGE="JavaScript1.2">
myFish = ["angel", "clown", "mandarin", "surgeon"];
document.writeln("myFish: " + myFish + "<BR>");
removed = myFish.splice(2, 0, "drum");
document.writeln("After adding 1: " + myFish);
document.writeln("removed is: " + removed + "<BR>");
removed = myFish.splice(3, 1)
document.writeln("After removing 1: " + myFish);
document.writeln("removed is: " + removed + "<BR>");
removed = myFish.splice(2, 1, "trumpet")
document.writeln("After replacing 1: " + myFish);
document.writeln("removed is: " + removed + "<BR>");
removed = myFish.splice(0, 2, "parrot", "anemone", "blue")
document.writeln("After replacing 2: " + myFish);
document.writeln("removed is: " + removed);
</SCRIPT>
This script displays:
myFish: ["angel", "clown", "mandarin", "surgeon"]
After adding 1: ["angel", "clown", "drum", "mandarin", "surgeon"]
removed is: undefined
After removing 1: ["angel", "clown", "drum", "surgeon"]
removed is: mandarin
After replacing 1: ["angel", "clown", "trumpet", "surgeon"]
removed is: drum
After replacing 2: ["parrot", "anemone", "blue", "trumpet", "surgeon"]
removed is: ["angel", "clown"]
Returns a string representing the array and its elements.
toString()
None.
The Array object overrides the toString method of Object. For Array objects, the toString method joins the array and returns one string containing each array element separated by commas. For example, the following code creates an array and uses toString to convert the array to a string.
var monthNames = new Array("Jan","Feb","Mar","Apr")
myVar=monthNames.toString() // assigns "Jan,Feb,Mar,Apr" to myVar
JavaScript calls the toString method automatically when an array is to be represented as a text value or when an array is referred to in a string concatenation.
In JavaScript 1.2 when you specify LANGUAGE="JavaScript1.2" in the <SCRIPT> tag, toString returns a string representing the source code of the array.
<SCRIPT LANGUAGE="JavaScript1.2">
var monthNames = new Array("Jan","Feb","Mar","Apr")
myVar=monthNames.toString() // assigns '["Jan", "Feb", "Mar", "Apr"]'
// to myVar
</SCRIPT>
Adds one or more elements to the beginning of an array and returns the new length of the array.
arrayName.unshift(element1,..., elementN)
The following code displays the myFish array before and after adding elements to it.
myFish = ["angel", "clown"];
document.writeln("myFish before: " + myFish);
unshifted = myFish.unshift("drum", "lion");
document.writeln("myFish after: " + myFish);
document.writeln("New length: " + unshifted);
This example displays the following:
myFish before: ["angel", "clown"]
myFish after: ["drum", "lion", "angel", "clown"]
New length: 4
pop, push, shift
Returns the primitive value of an array.
valueOf()
None
The Array object inherits the valueOf method of Object. The valueOf method of Array returns the primitive value of an array or the primitive value of its elements as follows:
This method is usually called internally by JavaScript and not explicitly in code.
Object.valueOf
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Last Updated: 11/13/98 10:22:45
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