An array is declared using square-bracketed notation as in the following:
var names = ["Abhi", "Ayush", "Abhijeet"]
To get an element put its index in square brackets (the first index is 0) as in the following:
var names = ["Abhi", "Ayush", "Abhijeet"]
alert(names[0])
alert(names[1])
alert(names[2])
We can also retrieve its length as in the following:
var names = ["Abhi", "Ayush", "Abhijeet"]
alert(names.length)
Methods pop and push
There is a method pop that removes the last item and returns it.
Here we will see how the “abhijeet” is being popped off.
var names = ["Abhi", "Ayush", "Abhijeet"]
alert("I remove " + names.pop())
// Now we have ["Abhi","Ayush"]
alert("Now length is: " + names.length) // Abhijeet is removed
There is another method push that appends an element to the array.
Let’s say we’ve forgotten Bittoo as in the following:
var names = ["Abhi", "Ayush"]
names.push("Bittoo");
// now got ["Abhi", "Ayush", "Bittoo"]
alert("Last element is:" + names[names.length - 1])
Iterating over an array
To iterate over elements, a loop over all indices is usually used as in the following:
var names = ["Ab", "Yogi", "Abhi", "Ayush", "Bittoo"]
for (var i = 0; i < names.length; i++) {
alert(names[i])
}
Multidimensional arrays
Here is an example:
var multi = [[10, 20, 30], [40, 50, 60], [70, 80, 90]]
alert(multi[1][1]) //it is central element
join and split
- The join method combines an array into a string using a specifeid separator as in the following:
var names = ["Ab", "Abhi", "Ayush", "Bittoo"];
var s = names.join(', ');
alert(s);
- The split method is the reverse of join:
var names = "Abhi,Ayush,Bittoo";
var ar = names.split(',');
// ar is ["Abhi", "Ayush", "Bittoo"]
alert(ar[0]);
Removing from an array
Here is an example:
var ar = ["Hello", "Most", "Welcome"]
delete ar[1]
// now ar = ["Hello", undefined, "Welcome"]
alert(ar[1]) // undefined
A delete operator removes a key-value pair. Basically because an array is just a hash, the slot becomes undefined.
We need to remove an item without leaving holes between indexes. For this there is another method known as a splice.
Method splice
Syntax
ar.splice(index, deleteCount[, elem1,..., elemN])
It can delete elements and replace them.
Here is an example:
var ar = ["Hello", "Most", "Welcome"]
ar.splice(1, 1) // remove 1st element starting at index 1
alert(ar.join(',')) // ["Hello", "Welcome"] (1st element removed)
Another example.
Splice is able to insert elements, just set the deleteCount to 0.
var ar = ["Hello", "Most", "Welcome"];
// from 2nd position
// delete 0
// and insert "Hi", "Buddy"
ar.splice(2, 0, "Hi", "Buddy")
alert(ar) // "Hello", "Most", "Hi", "Buddy", "Welcome"
Method slice
We can also extract a portion of array using slice(begin, end).
This method does not modify the array, it just copies a slice of it.
Example
var ar1 = ["Hello", "Most", "Welcome"];
var ar2 = ar1.slice(0, 2) // take 2 elements starting at 0
alert(ar2.join(', ')) // "Hello, Most"
Method reverse
Suppose I want the last part of a domain, like “com” from “www.abhijeet.com”.
Example
var domname = "www.abhijeet.com"
var l = domname.split('.').reverse()[0]
alert(l)