JavaScript Array Object shift() and unshift()

JavaScript Array Object Methods – Part II

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JavaScript Array Object Methods – Part II
JavaScript Array Object shift() and unshift()

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shift():

As the pop() method removes and returns the last element, the shift() method removes and returns the first element of an array object. Since the first element is removed and returned this also affects the length of the array.

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

arrayObject.shift()

Example

<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.shift() + "<br />")
         document.write(exforsys)
      </script>
   </body>
</html>

The output of the code above will be:

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

In the above example, the array object exforsys elements are first outputted and the shift() method is then used with the array object exforsys which removes and returns the first element of the array object exforsys (Training). The next document statement prints the array without the first element since it has been removed out in the previous statement.

unshift():

If a programmer wants to add one or more elements to the end of the array, he can use the push() method of the array object. There may be situations where a programmer might wish to add one or more elements to the beginning of the array. This can be achieved by using the unshift() method of the array object. The unshift() method of an array object is used to add one or more elements to the beginning of an array and returns the new length.

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

arrayObject.unshift(newelement1,newelement2,....,newelementn)

The newelement1, newelement2,...., newelementn represents the new elements to be added to the array object. It is required that at least newelement1 must be present. This means there must be at least one element specified in argument of the unshift() method to be added. The newelement2,....,newelementn are optional.

Example

<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.unshift("Welcome
         Message")+"<br />")
         document.write(exforsys)
      </script>
   </body>
</html>

The output of the code above will be:

Welcome,To,Exforsys,Training
5
Welcome Message,Welcome,To,Exforsys,Training

In the above example, the array object exforsys elements are first outputted and then the unshift method() used with the exforsys array object has in its argument "Welcome Message". This is added to the beginning of the array object exforsys and changes the length of the array exforsys to 5. This prints and the new array with "Welcome Message" added to the beginning of the array is outputted.

shift():

arrayObject.shift()

unshift():

arrayObject.unshift(newelement1,newelement2,....,newelementn)

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