JavaScript Array Object Methods – Part I | IT Training and Consulting

JavaScript Array Object Methods – Part I

In this JavaScript tutorial, you will learn about Array Object Methods – concat(), join(), pop(), push() and reverse() methods along with general syntax and examples.

concat()

The concat() method is used to join two or more Array objects together to produce a new one. In the concat() method, the original Array objects are unaffected by this method and only a copy of the new concatenated array is returned.

General syntax of the concat() method of the Array object of JavaScript:

arrayObject.concat(arrayname1,arrayname2,……,arraynamen)

An example to understand this concept in detail:

<html>
   <body>
      <script type="text/javascript">
          var exforsys = new Array(3)
          exforsys[0] = "Welcome"
          exforsys[1] = "To"
          exforsys[2] = "Training"
          var example = new Array(3)
          example[0] = "Given"
          example[1] = "By"
          example[2] = "Exforsys"
          document.write(exforsys.concat(example))

      </script>
   </body>
</html>

The output of the above example is

Welcome To Training Given By Exforsys

The concat() method has an argument, the array object example is concatenated with the array object exforsys.

join()

The join()method is used to join all the elements of an array into a single string. The elements are separated by an optional string separator specified in the join() method. If no string separator is specified in the join() method, then the default string separator used is comma.

General syntax of the join() method of the Array object of JavaScript:

arrayObject.join(separator)

The separator specified in argument is optional and a comma is used as a separator.

An example to understand this concept in detail:

<html>
   <body>
      <script type="text/javascript">
          var exforsys = new Array(4)
          exforsys[0] = "Welcome"
          exforsys[1] = "To"
          exforsys[2] = "Training"
          exforsys[3]= "Exforsys"
          document.write(exforsys.join() + "<br />")
          document.write(exforsys.join("!"))

      </script>
   </body>
</html>

The output of the above example is

Welcome,To,Training
Welcome!To!Training

In the first document.write statement has no separator argument given in the argument of the join() method of the array object exforsys and the default separator, the comma is used in output. In the second document.write statement of the above example the separator argument given in the argument of the join() method of the array object exforsys is ! and so this is used in output.

pop()

The method pop() is used to remove and return the last element of an array and therefore the length of the array object gets changed by this method.

General syntax of the pop() method of the Array object of JavaScript:

arrayObject.pop()

Let us see an example to understand this concept in detail:

<html>
   <body>
      <script type="text/javascript">
           var exforsys = new Array(4)
           exforsys[0] = "Welcome"
           exforsys[1] = "To"
           exforsys[2] = "Exforsys"
           exforsys[3] = "Training"
           document.write(exforsys + "<br />")
           document.write(exforsys.pop() + "<br />")
           document.write(exforsys)

      </script>
   </body>
</html>

The output of the above example is

Welcome,To,Exforsys,Training
Training
Welcome,To,Exforsys

In the above example, the array object exforsys elements are first outputted and the pop() method is used with the array object exforsys. This removes and returns the last element of the array object exforsys (Training). Then the next document statement prints the array without the last element since it has been popped out in the previous statement.

push()

push() method of an array object contrasts to the pop() method. push() method is used to add one or more elements to the array. This is added to the end of the array, changing the length of the array object. The new length is returned by the push() method.

General syntax of the push() method of the Array object of JavaScript:

arrayObject.push(element1,element2,….,elementn)

Here element1, element2,…., elementn represents the new elements to be added to the array object. It is required that at least element1 must be present. This means, in order for it to be added, there must be at least one element specified in argument of the push().

An example to understand this concept in detail:

<html>
   <body>
      <script type="text/javascript">
       var exforsys = new Array(4)
       exforsys[0] = "Welcome"
       exforsys[1] = "To"
       exforsys[2] = "Exforsys"
       exforsys[3] = "Training"
       document.write(exforsys + "<br />")
       document.write(exforsys.push("Good Day") + "<br />")
       document.write(exforsys)

      </script>
   </body>
</html>

The output of the code above will be:

Welcome,To,Exforsys,Training
5
Welcome,To,Exforsys,Training,Good Day

In the above example, the array object exforsys elements are first outputted and then the push() method with arguments as "Good Day" is used with the array object exforsys. This adds the element after the last element. Therefore, the length of the array changes to 5 and this is then outputted. As shown in the last result, the array is printed with the new elements added to it.

reverse()

As the name implies, the reverse() method of the Array object reverses the order of the elements in an array, using the first element as the last element and the last element as the first element. The original array is changed by using the reverse() method.

General syntax of the reverse() method of the Array object of JavaScript:

arrayObject.reverse()

An example to understand this concept in detail:

<html>
   <body>
      <script type="text/javascript">
         var exforsys = new Array(4)
         exforsys[0] = "Welcome"
         exforsys[1] = "To"
         exforsys[2] = "Exforsys"
         exforsys[3] = "Training"
         document.write(exforsys + "<br />")
         document.write(exforsys.reverse()
         + "<br />")

      </script>
   </body>
</html>

The output of the code above will be:

Welcome,To,Exforsys,Training
Training,To,Exforsys,Welcome

In the above example first the elements of the array object exforsys is printed as such and then the reverse() method is sued with the exforsys array object and so the first element "Welcome" is made as the last element and the last element "Training" is made as the last first element and changed array is printed

JavaScript Array Object Methods – Part I