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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>
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The output of the above example is
Welcome To Training Given By Exforsys
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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>
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The output of the above example is
Welcome,To,Training
Welcome!To!Training
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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>
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The output of the above example is
Welcome,To,Exforsys,Training
Training
Welcome,To,Exforsys
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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.
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