JavaScript Operator Program Flow


To corporate interactivity in the application you can use control flow statements. JavaScript supports a number of statements that is specially for controlling the program flow.

The first one is the selection structure. With this one you can create a junction in the code like and specify alternate course of program flow. In JavaScript there are four selection structures.

  • single-selection structure (if),
  • double-selection structure (if/else),
  • inline ternary operator ?:
  • multiple-selection structure (switch).

The repetition type is the second control structure type in JavaScript and when using one of those an action will be repeated as long as a condition is equal to true. In JavaScript there are four repetition structures.

  • expression is tested at the top of the loop (while),
  • expression is tested at the bottom of the loop (do/while),
  • operate on each of an object's properties (for/in).
  • counter controlled repetition (for).

Learn more about JavaScript Operators

Using Conditional Statements

The if and if...else conditional statements are used to test a condition. If the condition meets the test the related JavaScript code will be executed.

JS JavaScript - Using Conditional Statements

function DoSomething(jump, run, leap, sleep) {
// The contition is true.
if (jump) {
    return "You are jumping";
}
 
// Both condition are true	
if (run == "long distance" && sleep == "after the run") {
    return "The run is over";
}
 
// One of the condition are true
if ((leap == "Yes") || (sleep == "On the weekend")) {
    return "I'm either leaping or sleaping";
}
else {
    return "See you later mate!!";
}
}

Using Conditional Operators

 

In JavaScript it is also support for using implicit conditional form.

JavaScript - Using Conditional Operators.

// The condition: (time >= 12)
// returns "Afternoon" if the condition is true
// returns "Morning" if the condition is false.
 
var time = 13;
var afternoonOrMorning = (time >= 12) ? "Afternoon" : "Morning";
 
alert(afternoonOrMorning); 
// Result: Afternoon

JavaScript For Loop

Repetitive execution is called looping or iteration and in JavaScript there are several ways to do that. We say that one iteration is one single execution of the loop and that loop is normally controlled by a variable test.

JS JavaScript - Using JavaScript For Loop

var animals = ["dog", "cat", "horse", "bird"];
var result = "";
var i;
 
for (i = 0; i < animals.length; i++) {
    result += animals[i] + " : ";
}
 
alert(result); // Result: dog : cat : horse : bird : 

Learn more about JavaScript Loop For

JavaScript While Loop

In JavaScript the while loop is similar to a for loop. The main difference is that a for loop have built in counter and an update expression. The while loop does not have that.

JS JavaScript - Using JavaScript While Loop

var result = "";
var counter = 0;
 
while (counter < 5) {
    result += counter + " : ";
    counter++;
}
 
alert(result); // The result is: 0 : 1 : 2 : 3 : 4 : 

Learn more about JavaScript Loop While

Since the while loop doesn't have an explicit built-in counter variable it's more vulnerable to infinite looping. Therefor make sure that you are very careful when you are using while loops.



JavaScript Do..While Loop

JavaScript also have support for the do...while loop. That is very similar to the while loop but when using do..while you are guaranteed that it is executed at least once. This is because the condition is not tested in the start of the loop but in the end.

JS JavaScript - JavaScript Do..While Loop

var result = ""
var counter = 0;
do {
    result += counter + " : ";
    counter++;
}
while (counter < 5);
 
alert(result); // Result: 0 : 1 : 2 : 3 : 4 :

Using Break and Continue

To stop a loop execution a break statement can be is used. To jump to the next iteration in a loop the continue statement can be used. When the continue statement is used the the rest of the code block is skipped.

JS JavaScript - Using the Break statement in a Loop

var result = "";
var counter;
 
for (counter = 0; counter < 5; counter++) {
if (counter === 2) {  break;  }
 
    result += counter + " : ";
}
 
alert(result); // Result: 0 : 1 :

Learn more about JavaScript break

How to use the continue statement.

JS JavaScript - Using the Continue statement in a Loop

var result = "";
var counter;
 
for (counter = 0; counter < 5; counter++) {
if (counter === 2) {  continue;  }
 
    result += counter + " : ";
}
 
alert(result); // Result: 0 : 1 : 3 : 4 :

Learn more about JavaScript Operator Precedence
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JavaScript is one of the 3 core language technologies of the World Wide Web that all web developers must learn:

1.      HTML to define the content of web pages.

2.      CSS to specify the layout of web pages.

3.      JavaScript to program the behavior of web pages.

JavaScript is a scripting or programming language that allows you to implement complex things on web pages. Every time a web page does more than just sit there and display static information for you to look at, displaying timely content updates, interactive maps, animated 2D/3D graphics, scrolling video jukeboxes, etc. − you can bet that JavaScript is probably involved.


The benefits of using JavaScript are:

1.      You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

2.      Immediate feedback to the visitors − They don't have to wait for a page reload to see if they have forgotten to enter something.

3.      Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

4.      Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.


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