JavaScript - Interview Questions and Answers

51) What is the role of a strict mode in JavaScript?

The JavaScript strict mode is used to generates silent errors. It provides "use strict"; expression to enable the strict mode. This expression can only be placed as the first statement in a script or a function. For example:

52) What is the use of Math object in JavaScript?

The JavaScript math object provides several constants and methods to perform a mathematical operation. Unlike date object, it doesn't have constructors. For example:

53) What is the use of a Date object in JavaScript?

The JavaScript date object can be used to get a year, month and day. You can display a timer on the webpage by the help of JavaScript date object.

  function display() {   var date=new Date();   var day=date.getDate();   var month=date.getMonth()+1;   var year=date.getFullYear();   document.write("<br>Date is: "+day+"/"+month+"/"+year);   } display(); 

54) What is the use of a Number object in JavaScript?

The JavaScript number object enables you to represent a numeric value. It may be integer or floating-point. JavaScript number object follows the IEEE standard to represent the floating-point numbers.

  function display() { var x=102;//integer value   var y=102.7;//floating point value   var z=13e4;//exponent value, output: 130000   var n=new Number(16);//integer value by number object   document.write(x+" "+y+" "+z+" "+n);   }    display(); 

55) What is the use of a Boolean object in JavaScript?

The JavaScript Boolean is an object that represents value in two states: true or false. You can create the JavaScript Boolean object by Boolean() constructor.

  function display() { document.writeln(10<20);//true   document.writeln(10<5);//false    }    display(); 

56) What is the use of a TypedArray object in JavaScript?

The JavaScript TypedArray object illustrates an array like a view of an underlying binary data buffer. There is any number of different global properties, whose values are TypedArray constructors for specific element types.

  function display() { var arr1= [1,2,3,4,5,6,7,8,9,10];           arr1.copyWithin(2) ;         document.write(arr1);   } display(); 

57) What is the use of a Set object in JavaScript?

The JavaScript Set object is used to store the elements with unique values. The values can be of any type i.e. whether primitive values or object references. For example:

  function display() { var set = new Set();   set.add("jQuery");   set.add("AngularJS");   set.add("Bootstrap");   for (let elements of set) {    document.writeln(elements+"<br>");   }    } display(); 

58) What is the use of a WeakSet object in JavaScript?

The JavaScript WeakSet object is the type of collection that allows us to store weakly held objects. Unlike Set, the WeakSet are the collections of objects only. It doesn't contain the arbitrary values. For example:

  function display() { var ws = new WeakSet();   var obj1={};   var obj2={};   ws.add(obj1);   ws.add(obj2);   //Let's check whether the WeakSet object contains the added object   document.writeln(ws.has(obj1)+"<br>");   document.writeln(ws.has(obj2));    }    display() 

59) What is the use of a Map object in JavaScript?

The JavaScript Map object is used to map keys to values. It stores each element as key-value pair. It operates the elements such as search, update and delete on the basis of specified key. For example:

  function display() { var map=new Map();   map.set(1,"jQuery");   map.set(2,"AngularJS");   map.set(3,"Bootstrap");   document.writeln(map.get(1)+"<br>");   document.writeln(map.get(2)+"<br>");   document.writeln(map.get(3));   } display(); 

60) What is the use of a WeakMap object in JavaScript?

The JavaScript WeakMap object is a type of collection which is almost similar to Map. It stores each element as a key-value pair where keys are weakly referenced. Here, the keys are objects and the values are arbitrary values. For example:

  function display() { var wm = new WeakMap();   var obj1 = {};   var obj2 = {};   var obj3= {};   wm.set(obj1, "jQuery");   wm.set(obj2, "AngularJS");   wm.set(obj3,"Bootstrap");   document.writeln(wm.has(obj2));    }    display(); 

Interview :: JavaScript