It is used to display the popup dialog box such as alert dialog box, confirm dialog box, input dialog box etc. An object of window is created automatically by the browser. The window object represents a window in browser. In other words, a closure is the local variables for a function which is kept alive after the function has returned. JavaScript allows you to declare a function within another function, and the local variables still can be accessible even after returning from the function you called. The variable with var keyword inside a function is treated as Local variable, and the variable without var keyword inside a function is treated a global variable. What would be the difference if we declare two variables inside a JavaScript, one with 'var' keyword and another without 'var' keyword ? When html document is loaded in the browser, it becomes a document object. The document object represents the whole html document. It checks equality only,ĭifference between Window object and document object Document object = means simple equal to, it compare two values only. It checks for equality as well as the type. Using the triple equals, the values must be equal in type as well. The 3 equal signs (=) mean 'equality without type coercion'.

Displaying popup windows and dialog boxes (like alert dialog box, confirm dialog box and prompt dialog box).

Build small but complete client side programs.

It is used to create interactive websites. All these are not possible using Html so for perform all these task at client side we use JavaScript. Using Html we can not run any logic on web browser like addition of two numbers, check any condition, looping statements(for, while), decision making statement(if-else) etc at client side. Using Html we can only design a web page. JavaScript is a object-based scripting language. It is widely used for client side validation. JavaScript Interview Questions What is JavaScript ?

Javascript interview questions