Answers: Simple functions requires lot of unnecessary code / boilerplate which can simplifies using arrow function. There are two types of comments in JavaScript. Below is the example for the same. It operates the elements such as search, update and delete on the basis of specified key. The JavaScript Translator (embedded in the browser) is responsible for translating the JavaScript code for the web browser. You need to place it inside the body tag of HTML. Below are three ways to defined variable in JS It has a relevant JavaScript which is to run in a server. They are declared dynamically at runtime. If an exception is thrown at try block, the control will shifts to catch block. For example: 3030 because 10+20 will be 30. The delete used to perform to delete the property of an object. Answer: This is used to access the Browser window. Answers: Exception handling is possible; and this can be achieved using the following keywords try, catch and finally. Using the global object window, we can access the browser. // [1, 2, 3, 4, 5, 6]. It is widely used for client-side validation. The default object of a browser is a window. Let's see a simple example: There are 3 ways to create an object in JavaScript. Below is the example for the same. It can be used to access and change the content of HTML. Answer: checks the current Object and Returns true, If the object of specified type. For example: The JavaScript WeakMap object is a type of collection which is almost similar to Map. It doesn't contain the arbitrary values. Undefined value: A value that is not defined and has no keyword is known as undefined value. Below are the ways to do the same. Answer: ”The shift() removes the first element from an array and return it.’’ On the otherhand, unshift() adds the given element at the start of an array.” The push() adds the given element at the end of the array. This callback function will be invoked later inside the passed function. Window is a global object which holds location , variables, functions, and history. The value can be resolved value or it can be a reason as well which tells why the value is not resolved. var mid = [3, 4]; For example: The JavaScript Map object is used to map keys to values. The following example illustrates the usage: No, Java and JavaScript are the two different languages. Answer: variable have first its own scope, parent scope and global sope. A simple example is. performs the action after specified time like calling function, evaluating expressions. It is different from Java language. According to research UI Developer has a market share of about 3.0%.So, You still have the opportunity to move ahead in your career in UI Developer. It stores each element as key-value pair. The debugger stops the execution of the program at the position it is applied. Yes, because it doesn't require web server's support for execution. All Rights Reserved. For an example strict mode will not allow to use a variable without declaring it. DOM stands for Document Object Model. For developers coming from JavaScript background, the process of developing web applications becomes easier. history.go(number) - The number may be positive for forward, negative for backward. The storage of cookies on the hard disk depends on the OS and the browser. Here, the keys are objects and the values are arbitrary values. The training on scripting language is given for developers and web designers. Answers: Undefined variables are those that are declared in the program but have not been given any value. Dear Readers, Welcome to AJAX Interview questions with answers and explanation. For example, consider an element which has click event attached, and its parent also has the same event handler attached to it. Notice that the space and percentage symbol are replaced with %20 and %25. GangBoard is one of the leading Online Training & Certification Providers in the World. The history object of a browser can be used to switch to history pages such as back and forward from the current page or another page. In JavaScript, we need closures when a variable which is defined outside the scope in reference is accessed from some inner scope. Answer: == checks only with data, but === checks data with datatype. Answers: Whenever a variable is defined outside the current scope is accessed from within some inner scope closure will be created. Now, we can start the flow of execution manually. Answer: The encodeURI is used to encode an URL by replacing special characters, like space, percent. You can create the JavaScript Boolean object by Boolean() constructor. For example: The JavaScript WeakSet object is the type of collection that allows us to store weakly held objects. It may be integer or floating-point. Local Variables – Function parameters and variable defined inside function know as local variable. It returns the substring from start_Index and the returns ‘length’ number of characters. Answers: Reduce – This is used to reduce output to single value. Because, delete removes only the value of the array element, not the entire element. © Copyright 2011-2018 www.javatpoint.com. It can be easily used in the place of an expression. Answers: This keyword refers to the object. Answers: These 20 solved AJAX questions will help you prepare for technical interviews and online selection tests during campus placement for freshers and job interviews for professionals. Named - These type of functions contains name at the time of definition. Closures, JS scope, hoisting, the JS object model, and more. forEach – It executes using the refer function for each element of the array, passing the array element as an argument.