break, continue, and label

The break and continue can be used in JavaScript with loop instrucxtions: for() and while() to stop or "jump over" loops.

The break statement

The break statement stops the execution of a repetitive instruction.
- Example, a for() loop is stoped with 'break':

<script>
//defined to run till x is 10
for(x=0; x<10; x++){
 document.write('<br> X is '+x);

 //stops completely the loop when x is 3
 if(x==3) break;
} 
</script>

In the same way you can use it with while():

<script>
var x =0;

//defined to run till x is 10
while(x <10){
 document.write('<br> X este '+x);

 //stops completely the loop when x is 3
 if(x==3) break;
 x++;
} 
</script>

The continue statement

The continue statement breaks one iteration (in the loop), if a specified condition occurs, and continues with the next iteration in the loop..
- This example skips the value of 1 and 3:

<script>
//defined to run from 0 to 5
for(x=0; x<5; x++){
 //skips the execution when x is 1 or 3
 if(x ==1 || x ==3) continue;
 document.write('<br> X ise '+x);
} 
</script>

In the same way you can use it with while():

<script>
var x =0;

//defined to run from 0 to 5
while(x <5){
 //skips the execution when x is 1 or 3
 if(x ==1 || x ==3){
 x++; //to increment when it jumps over iteration
 continue;
 }

 document.write('<br> X este '+x);
 x++;
} 
</script>

JS label statements

label statements can be used in JavaScript with 'break' or 'continue'. It labels a group of nested repetitive instructions, allowing control over that group inside the nested instructions.

Syntax:

label_name:
for(...){
 //other instructions with for() or while()
}

- 'label_name' can be any name (except the reserved JavaScript keywords), followed by : and the nested group of for() or while().

Studying the following example, you can better understand how the 'label' it works:

<script>
loopX: //labels the next set of nested instructions
for(var x=0; x<5; x++){
 document.write('<h4>X - '+x+'</h4>');
 for(var y=0; y<3; y++){
 //stops execution of the entire group when x is 2
 if(x ==2) break loopX;

 document.write('<br>Y = '+y);
 }
}
</script>

- Testing the code, you will see that though 'break' is inside the second 'for()', by specifying 'loopX', which is the label of the entire set of nested instructions, it will stops the execution of entire group.

<<-While loops -- Alert, Confirm and Prompt->>

Daily Test with Code Example

HTML

CSS

JavaScript

PHP-MySQL

Which tag is used to add lists into <ul> and <ol> elements?

<ul>
 <li>http://coursesweb.net/html/</li>
 <li>http://coursesweb.net/css/</li>
</ul>

Which value of the "display" property creates a block box for the content and ads a bullet marker?

block list-item inline-block

.some_class {
  display: list-item;
}

Which instruction converts a JavaScript object into a JSON string.

JSON.parse() JSON.stringify eval()

var obj = {
 "courses": ["php", "javascript", "ajax"]
};
var jsonstr = JSON.stringify(obj);
alert(jsonstr);    // {"courses":["php","javascript","ajax"]}

Indicate the PHP class used to work with HTML and XML content in PHP.

stdClass PDO DOMDocument

$strhtml = '<body><div id="dv1">CoursesWeb.net</div></body>';
$dochtml = new DOMDocument();
$dochtml->loadHTML($strhtml);
$elm = $dochtml->getElementById("dv1");
echo $elm->nodeValue;    // CoursesWeb.net