Quiz
Javascript - Quiz - Jan 2016
This quiz has a time limit, so it opens in the usual player.
Questions in this quiz (15)
1What are the values that evaluate to false when used in a Boolean expression?
- AOnly null
- BOnly undefined
- COnly “”
- DOnly NaN
- EAll of the above
2Which of the following statements are TRUE?
- AWhen a variable that is not declared is used it returns “undefined”
- BWhen a variable that is not declared is used it throws ReferenceError
- CA function that is defined below in the later part of the script can be invoked / referred
- DA variable that is not assigned any value returns “undefined”
3What are the primitive types in Javascript?
- AInt, float, double, char, Boolean
- BInt, float, double, char, String, Boolean
- CNumber, String, Boolean
- DNumber, char, String, Boolean
4How do you create an Object with a prototype object assigned to variable “proto”?
- Avar myObject = new Object(proto);
- Bvar myObject = new Object();
myObject.prototype = proto; - Cvar myObject = Object.create(proto);
- Dvar myObject[“prototype”] = proto;
5How to create a Javascript array?
- AOnly var myArray = new Array();
- BOnly var myArray = [];
- Cvar myArray[] = new Object();
- DBoth a & b
6How do you invoke parent class’ constructor (by name ParentClass) from a sub class constructor (by name SubClass) to inherit properties defined in ParentClass in the new SubClass object?
- Afunction SubClass() { super(); }
- Bfunction SubClass() { ParentClass(); }
- Cfunction SubClass() { new ParentClass(); }
- Dfunction SubClass() { ParentClass.apply(this, arguments); }
- EAll of the above
7How do you use function to create a singleton object?
- Avar mySingleton = function() {
function SingletonClass() {
}
return new SingletonClass();
}; - Bb. var mySingleton = (function() {
function SingletonClass() {
}
return new SingletonClass();
})(); - Cvar mySingleton = {};
- DIt is not possible to create a singleton object using function
- Avar mySingleton = function() {
8What is a Closure?
- AA special scope variable assigned to function that holds states / variables that was accessible at the time of defining this inner function
- BClosure is a property of function that needs to be explicitly assigned within the body of function
- CClosure is a global function along with global variables
- DClosure is an inner function along with global variables
9How do you invoke a callback function within a loop with loop index variable as argument after 500 milliseconds?
- Afunction invokeCallback(callback) {
for(var i=0;i<5;i++) {
setTimeout(callback(i), 500);
}
} - Bfunction invokeCallback(callback) {
for(var i=0;i<5;i++) {
setTimeout(function() {callback(i)}, 500);
}
} - Cfunction invokeCallback(callback) {
function invoker(i) {
return function() { callback(i); }
}
for(var i=0;i<5;i++) {
setTimeout(invoker(), 500);
}
} - DNone of the above
- Afunction invokeCallback(callback) {
10How do you add a function “removeDuplicates” (already defined with this name) accessible from all Array objects?
- AArray.removeDuplicates = removeDuplicates;
- BArray.prototype.removeDuplicates = removeDuplicates
- Cvar myArray = new Array() {
this.removeDuplicates = removeDuplicates;
} - DArray is a predefined type in javascript. It cannot be modified.
11How does Javascript object inherit properties and methods defined in ancestor classes?
- AThrough constructor inheritance
- BUsing extends keyword
- CThrough prototype chaining
- DThere is no automatic support in Javascript. Properties and behaviors need to be explicitly added
12What is the difference between “!=” and “!==”?
- A“!==” will not check for null or undefined or “” while “!=” checks
- B“!=” does not convert type while “!==” does convert type
- C“!==” does not do type coercion while “!= does type coercion
- DBoth operators are same
13How do you pass JSON data as part of HTTP POST request body in AJAX request?
- Axhr.send(JSON.stringify(myJsonObject));
- Bxhr.open(‘post’, myUrl, JSON.stringify(myJsonObject));
- Cxhr.open(JSON.stringify(myJsonObject));
- Dxhr.open(‘post’, myUrl + “?” +
JSON.stringify(myJsonObject));
14How do you create a “div” element with id “childDiv” and append it to parent div with id “parentDiv” using DOM API?
- Avar childDiv = window.createElement(“div”);
window.getElementById(“parentDiv”).appendChild(childDiv); - Bvar childDiv = document.newElement(“div”);
document.getElementById(“parentDiv”).appendChild(childDiv); - Cvar childDiv = document.createElement(“<div
id=”childDiv”);
window.getElementById(“parentDiv”).appendChild(childDiv); - Dvar childDiv = document.createElement(“div”);
childDiv.setAttribute(“id”, “childDiv”);
document.getElementById(“parentDiv”).appendChild(childDiv);
- Avar childDiv = window.createElement(“div”);
15Choose the best practices that need to be adopted in production environment to improve the performance?
- AKeep Javascript files separate and download them individually
- BConcatenate multiple javascript files into single javascript file and refer to this javascript in the script tag
- CUse descriptive variable names and detailed comments
- DMinify javascript to reduce the overall size of Javascript file downloaded by browser
- EUse CDN site over local Javascript files
Information
- Description
- Javascript Quiz for emids participants
- Author
- arunram.krish
- Language
- English
- Views
- 496
- Tags
- Rating
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