JavaScript Interview Questions(5)

灰太狼 2023-09-25 19:27 45阅读 0赞

# 1.What are the pop-up boxes available in JavaScript? #

*  Alert Box
 *  Confirm Box
 *  Prompt Box

> Example of alert() in JavaScript

> Example of confirm() in JavaScript

> Example of confirm() in JavaScript

> Example of prompt() in JavaScript

# 2.How can we detect OS of the client machine using JavaScript? #

The navigator.appVersion string can be used to detect the operating system on the client machine.

# 3.How to submit a form using JavaScript by clicking a link? #

# 4.How to change the background color of HTML document using JavaScript? #

# 5.How to handle exceptions in JavaScript? #

*  By the help of `try/catch block`, we can handle exceptions in JavaScript.
 *  JavaScript supports try, catch, finally and throw keywords for exception handling.

# 6. How to validate a form in JavaScript? #

# 7.How to validate email in JavaScript? #

There are many criteria that need to be follow to validate the email id such as:

*  email id must contain the @ and . character
 *  There must be at least one character before and after the @.
 *  There must be at least two characters after . (dot).

# 8.What is this keyword in JavaScript? #

*  The this keyword is a reference variable that refers to the current object.

var address=    
    {
            
    company:"Javatpoint",    
    city:"Noida",    
    state:"UP",    
    fullAddress:function()    
    {
            
    return this.company+" "+this.city+" "+this.state;    
    }    
    };    
    var fetch=address.fullAddress();    
    document.writeln(fetch);

# 9.What is the requirement of debugging in JavaScript? #

*  JavaScript didn’t show any error message in a browser.
 *  However, these mistakes can affect the output.
 *  The best practice to find out the error is to debug the code.
 *  The code can be debugged easily by using web browsers like Google Chrome, Mozilla Firebox.  
    To perform debugging, we can use any of the following approaches:
 *  Using console.log() method
 *  Using debugger keyword

# 10.What is the use of debugger keyword in JavaScript? #

*  JavaScript `debugger` keyword sets the `breakpoint` through the code itself.
 *  The debugger `stops the execution of the program`at the position it is applied.
 *  we can start the flow of execution manually.
 *  If an exception occurs, the execution will stop again on that particular line…

function display()  
    {
          
    x = 10;    
    y = 15;    
    z = x + y;    
    debugger;    
    document.write(z);    
    document.write(a);     
    }     
    display();