How to define array length in javascript

In JavaScript, you can use the length attribute to define the length of the array, and the syntax format is "arrayObject.length". For regular arrays that have consecutive elements and start with element 0, the length attribute declares the number of elements in the array.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

Define array:

Array objects are used to store a series of values ​​in separate variable names.

We use the keyword new to create an array object. The following code defines an array object named myArray:

var myArray=new Array()

There are two ways to assign values ​​to an array (you can add as many values ​​as you want, just like you can define as many variables as you need ).

1. Define the array first and then assign the value:

var mycars=new Array()
mycars[0]="Saab"
mycars[1]="Volvo"
mycars[2]="BMW"

You can also use an integer independent variable to control the length of the array:

var mycars=new Array(3)
mycars[0]="Saab"
mycars[1]="Volvo"
mycars[2]="BMW"

2. Define the array and assign the value at the same time:

var mycars=new Array("Saab","Volvo","BMW")

length Property: The

length property sets or returns the number of elements in an array.

Syntax:

arrayObject.length

Description:

The length property of an array is always 1 greater than the subscript of the last element defined in the array. For regular arrays with consecutive elements starting with element 0, the length property declares the number of elements in the array.

The length property of an array is initialized when the array is created using the constructor Array(). When a new element is added to the array, the value of length is updated if necessary.

Set the length property to change the size of the array. If set to a value smaller than its current value, the array will be truncated and its trailing elements will be lost. If the set value is greater than its current value, the array will grow and new elements will be added to the end of the array, with their value being undefined.

Define the array length and output:

<script type="text/javascript">
var arr = new Array(3)
arr[0] = "John"
arr[1] = "Andy"
arr[2] = "Wendy"
document.write("Original length: " + arr.length)
document.write("<br />")
arr.length=5
document.write("New length: " + arr.length)
</script>

Output:

Original length: 3
New length: 5

[Recommended learning: javascript advanced tutorial]

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