IES: JS-deck 4 Flashcards

Question 1

Q

JS “native”

Answer

A

JS keyword
JS significant: avoid for variable/function names
In JavaScript, there’s no native keyword: the term “native JavaScript” is often used to describe:
Built-in functionalities:
Features and objects that are part of the JavaScript language itself or are provided by the JavaScript engine without requiring external libraries or frameworks.
Vanilla JavaScript: Code written without the use of external libraries or frameworks.

Question 2

Q

JS “new”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used to create an object.
Example
Employee obj = new Employee ();

Question 3

Q

JS “null”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used to represent a special data type no value.
Example

var age = null;
alert(age);

Question 4

Q

JS “package”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used to identify java classes and to execute the java method in a javascript.
Example
inBlock['package'] = something;

Question 5

Q

JS “private”

Answer

A

JS keyword
JS significant: avoid in variable/function names
IS an access modifier can be used with attributes, classes, constructors and methods which make it not accessible to other classes.
Example

public class Employee {
private String efn = "Joseph";
}
class MainClass {
public static void main(String[] args) {
Employee obj = new Employee ();
System.out.println("Name= " + obj.efn + " " + obj.lname);// gives error
}
}

Question 6

Q

JS “protected”

Answer

A

JS keyword
JS significant: avoid in variable/function names
An access modifier can be used with attributes, classes, constructors and methods which make it not accessible to other classes.
Example

Question 7

Q

JS “public”

Answer

A

JS keyword
JS significant: avoid in variable/function names
In JS, the concept of public is not a keyword: by default, all members (properties and methods) of a class are public cooling: you don’t need any special keyword to declare them.
Example

class Person {
  constructor(name, age) {
    this.name = name; *// Public property*
    this.age = age; *// Public property*
  }

  greet() { *// Public method*
    console.log(`Hello, my name is ${this.name}`);
  }
}

const john = new Person("John", 30);
console.log(john.name); *// Accessing public property*
john.greet(); **// Calling public method**

Question 8

Q

JS “return”

Answer

A

JS keyword
JS significant: avoid for variable/function names
In JavaScript, the return keyword is used to specify the value that a function should output or “return” back to the caller.
When a return statement is encountered within a function, the function immediately stops executing, and the specified value (if any) is sent back to the code that called the function.
You can use return to return a value from a function. This allows you to use the result of the function’s computations in other parts of your code.
If you don’t specify a value after the return keyword, or if you omit the return statement altogether, the function will return undefined.
Example

function addNumbers(num1, num2) {
  return num1 + num2; 
}

let result = addNumbers(3, 5); 
console.log(result); // Output: 8

Question 9

Q

JS “short”

Answer

A

JS keyword
JS significant: avoid for variable/function names
Belongs to the so-called future keywords by the ECMAScript specification. Has no special functionality at present but might at some future time.
In ECMAScript 5/6, short was removed from the list of reserved words. Nonetheless for compatibility with older browsers not implementing either, you shouldn’t use it anyway.

Question 10

Q

JS “static”

Answer

A

JS keyword
JS significant: avoid for variable/function names
Used to define a static method in a class. Static methods are those methods that are not called on the object.
Example

class Employee extends Person {
constructor(name, eid, salary) {
super(name);
}
static disp()
{
return "This is static method "
}
}
document.writeln( Employee.disp()  );

Question 11

Q

JS “super”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used to call function or method of a parent class.
Example
super.disp(); //the disp is a method of a parent class

Question 12

Q

JS “switch”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used in a switch-case construct, where switch evaluates an expression.
Example

var date = new Date();
switch(date.getDay()) {
case 6:
alert("This is weekend.");
break;
case 0:
alert("This is weekend.");
default:
alert("Looking for a weekend.");
break;
}

Question 13

Q

JS “synchronized”

Answer

A

JS keyword
JS significant: avoid for variable/function names
JavaScript does not have a synchronized keyword
JavaScript is single-threaded. This eliminates the need for explicit synchronization

Question 14

Q

JS “this”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used to refer to the current object.
Example

class Employee extends Person {
constructor(name, eid, salary) {
super(name);
}
get incsalary() {
return this.salary * 0.2;
}
}

Question 15

Q

JS “throw”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used in a try block to explicitly throw an exception object.
Example

Var i=1
try {
if(i == "") throw "is Empty";
if(x > 0) throw "positive";
if(x < 0) throw "negative";
}
catch(msg) {
message.innerHTML = "Input " + msg;
}

Question 16

Q

JS “throws”

Answer

A

JS keyword
JS significant: avoid for variable/function names
In JavaScript, there is no throws keyword.
JavaScript uses throw for error handling (used to explicitly throw an exception (error) in your code)

Question 17

Q

JS “transient”

Answer

A

JS keyword
JS significant: avoid for variable/function names
In JS, there is no transient keyword: JS doesn’t have the concept of serialization: when you want to store or transmit data in JS, you typically use JSON.
if you want to exclude certain properties from a JSON representation of an object in JS,
Example
Manually delete them:

const obj = {
  name: "John",
  age: 30,
  password: "secret"
};

delete obj.password; // Remove the password property

const jsonString = JSON.stringify(obj); // Convert to JSON

Use a custom serialization function:

function customToJSON(obj) {
  const result = {};
  for (const key in obj) {
    if (key !== "password") {
      result[key] = obj[key];
    }
  }
  return result;
}

const jsonString = JSON.stringify(obj, customToJSON);

Question 18

Q

JS “true”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used to store or represent primitive data type Boolean ‘true’.
Example
var inp = true;

Question 19

Q

JS “try”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Used for exception handling to check a block of code for errors.
Example

Var i=1
try {
if(i == "") throw "is Empty";
if(x > 0) throw "positive";
if(x < 0) throw "negative";
}
catch(msg) {
message.innerHTML = "Input " + msg;
}

Question 20

Q

JS “typeof”

Answer

A

JS keyword
JS significant: avoid in variable/function names
Which used to return the data type of an operand.
Example
typeof("hello") // output as string