Javascript Loops
JavaScript For Loop
In JavaScript, there are two different kind of loops:
{
code to be executed
}
Note: The increment parameter could also be negative, and the <= could be any comparing statement
Example
<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=5;i++)
{
document.write("The number is " + i);
document.write("<br />");
}
</script>
</body>
</html>
Javascript While Loop
while (variable<=endvalue)
{
code to be executed
}
Note: The <= could be any comparing operator.
Example
<html>
<body>
<script type="text/javascript">
var i=0;
while (i<=5)
{
document.write("The number is " + i);
document.write("<br />");
i++;
}
</script>
</body>
</html>
{
code to be executed
}
while (variable<=endvalue);
Example
<html>
<body>
<script type="text/javascript">
var i=0;
do
{
document.write("The number is " + i);
document.write("<br />");
i++;
}
while (i<=5);
</script>
</body>
</html>
Javascript Break Loop
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>
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 For in Statement
{
code to be executed
}
Note: The code in the body of the for...in loop is executed once for each property.
Example
var person={fname:"John",lname:"Doe",age:25};
for (x in person)
{
document.write(person[x] + " ");
}
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JavaScript For Loop
Loops execute a block of code a specified number of times, or while a specified condition is true.
JavaScript Loops
Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.In JavaScript, there are two different kind of loops:
- for - loops through a block of code a specified number of times
- while - loops through a block of code while a specified condition is true
The for Loop
The for loop is used when you know in advance how many times the script should run.Syntax
for (variable=startvalue;variable<=endvalue;variable=variable+increment){
code to be executed
}
Example
The example below defines a loop that starts with i=0. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs.Note: The increment parameter could also be negative, and the <= could be any comparing statement
Example
<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=5;i++)
{
document.write("The number is " + i);
document.write("<br />");
}
</script>
</body>
</html>
Javascript While Loop
Loops execute a block of code a specified number of times, or while a specified condition is true.
The while Loop
The while loop loops through a block of code while a specified condition is true.Syntax
while (variable<=endvalue)
{
code to be executed
}
Note: The <= could be any comparing operator.
Example
The example below defines a loop that starts with i=0. The loop will continue to run as long as i is less than, or equal to 5. i will increase by 1 each time the loop runs:Example
<html>
<body>
<script type="text/javascript">
var i=0;
while (i<=5)
{
document.write("The number is " + i);
document.write("<br />");
i++;
}
</script>
</body>
</html>
The do...while Loop
The do...while loop is a variant of the while loop. This loop will execute the block of code ONCE, and then it will repeat the loop as long as the specified condition is true.Syntax
do{
code to be executed
}
while (variable<=endvalue);
Example
The example below uses a do...while loop. The do...while loop will always be executed at least once, even if the condition is false, because the statements are executed before the condition is tested:Example
<html>
<body>
<script type="text/javascript">
var i=0;
do
{
document.write("The number is " + i);
document.write("<br />");
i++;
}
while (i<=5);
</script>
</body>
</html>
Javascript Break Loop
The break Statement
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>
The continue Statement
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 For in Statement
JavaScript For...In Statement
The for...in statement loops 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 property.
Example
Looping through the properties of an object:Example
var person={fname:"John",lname:"Doe",age:25};
for (x in person)
{
document.write(person[x] + " ");
}
Next Class -->>
great
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