Dev Corner » JavaScript

Join (concatenate) strings in JavaScript

bateto — Wed, 07 Oct 2009 15:54:35 +0000

Problem

How to join together two strings and how to make one long string from numerous pieces?

Solution

For the purpose of a single statement, use the plus (+) operator to concatenate multiple strings.

var longString = "One piece " + "plus one more ";

To compose a string value in multiple statements, use the operator +=

var sentence = "";
sentence += "word1 ";
sentence += "word2 ";
sentence += "word3";

We can also use and the plus for this operation, but its less elegant:

var sentence = "word1 word2 word3";

Find the type of an element in JavaScript

bateto — Sun, 04 Oct 2009 21:43:54 +0000

Sometimes we should find what the is the type of a given variable. In JavaScript there is a simple way to solve this problem - using the operator typeof. This operator returns as result of the check a string, which could have one of the listed values:

number
string
boolean
object
function
undefined

Example #1

typeof(123);			//This will return number
typeof("abd");			//This will return string
typeof(false);			//This will return boolean
 
 
typeof(typeof(var));		
//This will return string - no matter what the type of var is

Sometimes it is possible that IE thinks that a function is actually an object.

Example #2

typeof(document.getElementById);			
//The possible result for this operation is object, instead of function

Hello JavaScript!

admin — Tue, 31 Mar 2009 07:50:56 +0000

How to implement the simplest JavaScript code ? – the explorer to alert with “Hello JavaScript!”

For this purpose we use the function alert(), which opens up a box with a message. In our example it’s “Hello JavaScript!”, but it could be everything.

<script type="text/javascript">
	window.alert("Hello JavaScript!");
script>

This function is very handy when there is a debugging process for a JavaScript. But be beware not to place it in a loop. Otherwise there would be a nasty alert for a lot of times, which could make you angry and you probably will have to press the “OK” button for a thousand times.