{"id":520,"date":"2014-10-06T12:46:37","date_gmt":"2014-10-06T20:46:37","guid":{"rendered":"http:\/\/www.tech.dimprash.com\/?p=520"},"modified":"2019-05-23T14:08:42","modified_gmt":"2019-05-23T22:08:42","slug":"javascript-set2-of-interview-questions","status":"publish","type":"post","link":"http:\/\/www.tech.dimprash.com\/?p=520","title":{"rendered":"Javascript Set2 of Interview questions"},"content":{"rendered":"

1) Does Javascript support read only attributes of Object? <\/strong><\/p>\n

With any javascript interpreter that implements ECMAScript 5 you can use Object.defineProperty to define readonly properties. In loose mode the interpreter will ignore a write on the property, in strict mode it will throw an exception.<\/p>\n

var obj = {};\r\nObject.defineProperty( obj, \"\", {\r\n  value: \"\",\r\n  writable: false,\r\n  enumerable: true,\r\n  configurable: true\r\n});\r\n<\/pre>\n
Also you can try to attempt this via private attributes simulation.<\/p>\n
2) What does the delete operator do ? <\/strong>
\ndelete is used to delete object properties. It will not delete ordinary variables defined with var. it will delete global variables though since they are actually properties of the global object.<\/p>\n
3) What are all the types of Pop up boxes available in JavaScript?<\/strong><\/p>\n
Alert
\nConfirm and
\nPrompt<\/p>\n
4) What does the void operator do<\/strong>
\nThe void operator is often used merely to obtain the undefined primitive value, usually using “void(0)” (which is equivalent to “void 0”). In these cases, the global variable undefined can be used instead (assuming it has not been assigned to a non-default value). undefined isn’t a JavaScript keyword, but a property of the global object. So it can be shawdowed sometimes. http:\/\/adripofjavascript.com\/blog\/drips\/javascripts-void-operator.html<\/p>\n
5) What does use strict in javascript do ? What kind of errors does it catch ? <\/strong>
\nIf you use “use strict” javascript will flag error for certain cases.<\/p>\n
x = 3.14; \/\/ will cause error since x is not declared
\nx = {p1:10, p2:20}; \/\/ using object without declaring it
\nvar x = 3.14; delete x; \/\/ deleting a variable will cause an error
\nfunction x(p1, p2) {}; delete x; \/\/ deleting a function will cause an error
\nfunction x(p1, p1) {}; \/\/ Duplicating parameter names will cause an error<\/p>\n
6) What is event bubbling and event capturing ?<\/strong>
\nEvent bubbling and capturing are two ways of event propagation in the HTML DOM API, when an event occurs in an element inside another element, and both elements have registered a handle for that event. The event propagation mode determines in which order the elements receive the event.<\/p>\n
With bubbling, the event is first captured and handled by the innermost element and then propagated to outer elements.<\/p>\n
With capturing, the event is first captured by the outermost element and propagated to the inner elements.<\/p>\n
We can use the addEventListener(type, listener, useCapture) to register event handlers for in either bubbling (default) or capturing mode. To use the capturing model pass the third argument as true<\/p>\n
The event handling process:<\/p>\n