Showing posts with label Statements. Show all posts
Showing posts with label Statements. Show all posts

JavaScript - Catching Errors
4:21 AM - Posted by Vipin C - 0 comments
When browsing Web pages on the internet, we all have seen a JavaScript alert box telling us there is a runtime error and asking "Do you wish to debug?". Error message like this may be useful for developers but not for users. When users see errors, they often leave the Web page.

The try...catch statement allows you to test a block of code for errors.


JavaScript For...In Statement
3:25 AM - Posted by Vipin C - 0 comments

The for...in statement loops through the elements of an array or through the properties of an object.

Syntax

for (variable in object)
  {
  code to be executed
  }
Note: The code in the body of the for...in loop is executed once for each element/property.
Note: The variable argument can be a named variable, an array element, or a property of an object.

Example

Use the for...in statement to loop through an array:

Example

<html>
<body>

<script type="text/javascript">
var x;
var mycars = new Array();
mycars[0] = "Saab";
mycars[1] = "Volvo";
mycars[2] = "BMW";

for (x in mycars)
  {
  document.write(mycars[x] + "<br />");
  }
</script>

</body>
</html>


Javascript continue Statement
3:23 AM - Posted by Vipin C - 0 comments
The continue statement will break the current loop and continue with the next value

Example

.
<html>
<body>
<script type="text/javascript">
var i=0
for (i=0;i<=10;i++)
  {
  if (i==3)
    {
    continue;
    }
  document.write("The number is " + i);
  document.write("<br />");
  }
</script>
</body>
</html>


Javascript break Statement
3:22 AM - Posted by Vipin C - 0 comments
The break statement will break the loop and continue executing the code that follows after the loop (if any).

Example



<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=10;i++)
  {
  if (i==3)
    {
    break;
    }
  document.write("The number is " + i);
  document.write("<br />");
  }
</script>
</body>
</html>


JavaScript Switch Statement
3:11 AM - Posted by Vipin C - 0 comments

Use the switch statement to select one of many blocks of code to be executed.

Syntax

switch(n)
{
case 1:
  execute code block 1
  break;
case 2:
  execute code block 2
  break;
default:
  code to be executed if n is different from case 1 and 2
}
This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically.

Example




<script type="text/javascript">
//You will receive a different greeting based
//on what day it is. Note that Sunday=0,
//Monday=1, Tuesday=2, etc.


var d=new Date();
theDay=d.getDay();
switch (theDay)
{
case 5:
  document.write("Finally Friday");
  break;
case 6:
  document.write("Super Saturday");
  break;
case 0:
  document.write("Sleepy Sunday");
  break;
default:
  document.write("I'm looking forward to this weekend!");
}
</script>


If Statement
11:14 PM - Posted by Vipin C - 0 comments

Use the if statement to execute some code only if a specified condition is true.

Syntax

if (condition)
{
code to be executed if condition is true
}

Note that if is written in lowercase letters. Using uppercase letters (IF) will generate a JavaScript error!

Example

<script type="text/javascript">
//Write a "Good morning" greeting if
//the time is less than 10

var d=new Date();
var time=d.getHours();

if (time<10)
  {
  document.write("<b>Good morning</b>");
  }
</script>


JavaScript Conditional Statements
11:13 PM - Posted by Vipin C - 0 comments

Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.

In JavaScript we have the following conditional statements:

  • if statement - use this statement to execute some code only if a specified condition is true
  • if...else statement - use this statement to execute some code if the condition is true and another code if the condition is false
  • if...else if....else statement - use this statement to select one of many blocks of code to be executed
  • switch statement - use this statement to select one of many blocks of code to be executed