Question 1
Question
What are the different ways in which you can create a javascript object? Choose ALL the right options
Answer
-
var object = { prop1: "value1", prop2 : "value2"};
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var object = new Object();
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var object = {};
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var object = Object.create({});
Question 2
Question
How to create a constructor function?
Answer
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Any function when prefixed with "new" keyword at the time of invocation acts like a constructor function.
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Name of the function should be "constructor"
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You have to assign a property named "constructor" and assign a function to it
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Constructor function cannot be created in javascript
Question 3
Question
How do you demonstrate inheritance in Javascript? Consider "BaseClass" is the name of the parent class and "SubClass" is the name of the sub-class.
Answer
-
class SubClass extends BaseClass { }
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function SubClass() {
BaseClass.apply(this, Array.prototype.slice.call(arguments, 0);
}
SubClass.prototype = Object.create(BaseClass.prototype);
-
function SubClass() {
BaseClass.apply(this, Array.prototype.slice.call(arguments, 0);
}
-
function SubClass() {
super(Array.prototype.slice.call(arguments, 0));
}
SubClass.prototype = Object.create(BaseClass.prototype);
Question 4
Question
When does a Closure scope gets created?
Answer
-
Every function has a Closure scope associated with it
-
Every time a inner function is defined within another function
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When an inner function is defined within another function and that refers to variables that are available at the defining function (local variables of enclosing functions and its parent right until global)
-
A closure keyword is available. When a variable is declared with that modifier, closure scope is created
Question 5
Question
How can I create a constant in Javascript 5?
Answer
-
const myConstant = 3.414;
-
var myConstant = { value : "3.414";}
-
var myConstant = new Object(3.414)
-
var myConstant = Object.create(null, { value: {
configurable : false,
writable : false,
enumerable : false,
value : 3.414
}
});
Question 6
Question
How does Javascript achieve Inheritance?
Answer
-
Inheritance using extends keyword
-
Inheritance through Constructor chaining
-
Inheritance through Prototype chaining
-
Inheritance achieved programmatically
Question 7
Question
Javascript does not support overriding?
Question 8
Question
It is a better practice (in terms of performance) to create deep inheritance and access methods in the ancestor classes.
Question 9
Question
It is possible to create namespaces in Javascript.
Question 10
Question
It is possible to implement Singleton pattern in javascript.
Question 11
Question
Every Javascript function is an object with the constructor as "Function"
Question 12
Question
How can I create immutable property in a javascript object?
Question 13
Question
How to ensure that a property in Javscript object is never removed or re-configured
Answer
-
Define the property with private modifier
-
It is not possible to stop removing the property from object
-
Every property defined using "Object.defineProperty" cannot be removed
-
Using Object.defineProperty and setting "configurable" to false
Question 14
Question
How can I avoid creating global variables and functions used most often for initialization?
Question 15
Question
How can I create Block - scoped variable in ES-6?
Answer
-
Using var
-
Using let
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Using const
-
Using def