IES: JS-deck 6 Flashcards

Question 1

Q

JS Object

Answer

A

JS significant: avoid for variable/function names
collection of key-value pairs, where the keys are strings (or symbols) and the values can be any data type (including other objects or functions)
fundamental building blocks in JS used to represent real-world entities, data structures, and more
a standalone entity, with properties and type
Examples
// Creating a JavaScript object using an object literal
~~~
const person = {
firstName: “John”,
lastName: “Doe”,
age: 30,
occupation: “Developer”,
~~~
** // Method within the object**
~~~
greet: function() {
console.log(Hello, my name is ${this.firstName} ${this.lastName}.);
}
};
~~~
// Accessing object properties
~~~
console.log(person.firstName); // Output: John
console.log(person.age); // Output: 30
~~~
// Calling the object method
person.greet(); // Output: Hello, my name is John Doe.

Question 2

Q

JS prototype

Answer

A

JS Object
JS significant: avoid for variable/function names
object from which other objects inherit properties and methods: a fundamental concept in JS’s object-oriented programming model.
allow properties and methods to be shared among instances of the function or object
Examples
// Constructor function
~~~
function Person(name, age) {
this.name = name;
this.age = age;
}
~~~
// Add a method to the prototype
~~~
Person.prototype.greet = function() {
console.log(Hello, my name is ${this.name} and I am ${this.age} years old.);
};
~~~
// Create instances of Person
~~~
const john = new Person(“John”, 30);
const jane = new Person(“Jane”, 25);
~~~
// Call the greet method on the instances
~~~
john.greet(); // Output: “Hello, my name is John and I am 30 years old.”
jane.greet(); // Output: “Hello, my name is Jane and I am 25 years old.”
~~~

Question 3

Q

JS String

Answer

A

JS Primitive data type (numbers, Booleans, etc.)
JS significant: avoid for variable/function names
are not technically objects but behave like them in many ways.
Are primitive without methods or properties whereas objects are complex data types.
Example
~~~
let str = “Hello World”;
// String primitive
console.log(typeof str); // Output: string
~~~

Question 4

Q

JS toString

Answer

A

JS Method
JS significant: avoid for variable/function names
Converts an object to a string representation: built-in method available on most JS objects-returns a string representation of the object
Syntax
object.toString();
Examples
1. Converting a number to a string:
~~~
let num = 10;
let str = num.toString();
console.log(str); // Output: “10”
console.log(typeof str); // Output: “string”
~~~
2. Converting an array to a string:
~~~
let fruits = [“Apple”, “Banana”, “Orange”];
let str = fruits.toString();
console.log(str); // Output: “Apple,Banana,Orange”
~~~
3. Converting an object to a string:
~~~
let person = {
name: “John”,
age: 30
};
let str = person.toString();
console.log(str); // Output: “[object Object]”
~~~
4. Customizing the toString() method:
~~~
function Person(name, age) {
this.name = name;
this.age = age;
}
Person.prototype.toString = function() {
return Name: ${this.name}, Age: ${this.age};
};
let john = new Person(“John”, 30);
console.log(john.toString()); // Output: “Name: John, Age: 30”
~~~
5. Using the Radix parameter (for Numbers):
~~~
let num = 10;
let binaryStr = num.toString(2); // Convert to binary
let hexStr = num.toString(16); // Convert to hexadecimal
console.log(binaryStr); // Output: “1010”
console.log(hexStr); // Output: “a”
~~~

Question 5

Q

JS undefined

Answer

A

JS primitive data type (numbers, Boolean, etc.)
JS significant: avoid for variable/function names
It represents the absence of a value: a primitive data type and special value indicating a variable has been declared but hasn’t been assigned a value.
Examples
~~~
let x; // x is declared but not assigned a value
console.log(x); // Output: undefined
~~~
```
function greet(name) {
console.log("Hello, " + name);
}
greet(); // Output: Hello, undefined 
// The parameter 'name' is not provided, so it's undefined
~~~
```
const obj = {};
console.log(obj.age); // Output: undefined
// The ‘age’ property does not exist on the object
~~~

Question 6

Q

JS valueOf

Answer

A

JS Method
JS significant: avoid for variable/function names
Retrieves the primitive value (like a number, string, or Boolean) of an object
Available on all JS objects-inherited from Object.prototype
often called automatically where a primitive value is expected such as math operations or comparison (rare, otherwise)
Examples
1. String object:
~~~
const strObj = new String(“Hello World”);
console.log(strObj.valueOf()); // Output: “Hello World”
~~~
2. Number object:
~~~
const numObj = new Number(10);
console.log(numObj.valueOf()); // Output: 10
~~~
3. Date Object:
~~~
const dateObj = new Date();
console.log(dateObj.valueOf()); // Output: Timestamp in milliseconds
~~~
4. Custom object:
~~~
function MyNumber(value) {
this.value = value;
}
MyNumber.prototype.valueOf = function() {
return this.value;
};
const myNum = new MyNumber(5);
console.log(myNum + 3); // Output: 8
~~~

Question 7

Q

HTML alert

Answer

A

HTML Window Object
JS significant: avoid for variable/function names
displays alert box with message and OK button
used to bring information through to user
Syntax:
alert(message)
Return value:
none
Examples:
1. Alert box with line-breaks:
alert("Hello\nHow are you?");
2. Alert the hostname of the current URL:
alert(location.hostname);

Question 8

Q

off

HTML all

Answer

A

HTML Property(CSS)
JS significant: avoid for variable/function names
JS significant: avoid for variable/function names
In CSS, the shorthand property setting all tags to initial or inherited values; or in some cases, sets values to another spreadsheet origin
Syntax:
all: initial|inherit|unset|revert|revert-layer;
Default value: none
Property values:
1. initial: set all properties to their default values
2. Inherit: set all properties to their inherited value.
3. unset: all element’s attributes updated to either original values if inherited by default or initial values if not.
4. revert: undo/restore previous state/value of property/setting
5. revert-layer: Reverse modifications made to specific layer, restoring to previous state/config. within software/system
Example: all: initial property
~~~
<!DOCTYPE html>

<html>
<head>
<title>
CSS all property
</title>

<style>

        h1,
        h3 {
            background-color: yellow;
            color: green;
            all: initial;
        }
        body {
            text-align: center;
            all: initial;
        }

</style>
</head>
<body>
<h1>GeeksforGeeks</h1>
<h3>all property</h3>
</body>
</html>

~~~

Question 9

Q

HTML anchor

Answer

A

HTML Name
JS significant: avoid for variable/function names
defines a hyperlink, used to link from one page to another.
most important attribute is href indicating link destination
Example
<a href="https://www.w3schools.com">Visit W3Schools.com!</a>

Question 10

Q

HTML anchors

Answer

A

HTML Name
JS significant: avoid for variable/function names
defines a hyperlink, used to link from one page to another.
most important attribute is href indicating link destination
Example
<a href="https://www.w3schools.com">Visit W3Schools.com!</a>

Question 11

Q

HTML area

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
defines an area inside an image map (an image map is an image with clickable areas).
always nested inside a <map> tag
Example
~~~
<img></img>

~~~

Question 12

Q

HTML assign

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
Assigns a source or source properties to a target
Example
// Assign Source to Target
Object.assign(person1, person2);

Question 13

Q

HTML blur

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
removes the keyboard focus from the current element: focus with the help of the focus() method
apply the blur to any element
Syntax
Object.blur()
Example
~~~

<html>
<head>
<title>HTML DOM blur() Method</title>
</head>
<body>
<h1>
GeeksforGeeks
</h1>
<h2>
DOM blur Property
</h2>
<input></input>
<br></br>
<br></br>
<button>Focus</button>
<button>Blur</button>

<script>
function inputFocus() {
			document.getElementById('txt').focus();
		}
		function inputBlur() {
			document.getElementById('txt').blur();
		}
</script>

</body>
</html>

~~~

Question 14

Q

HTML button

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
Tag defines clickable button
Inside <button> put text (and tags like <i>, <b>, <strong>, <br>, <img>, etc.): not possible with <input> button
always specify <button> type attribute: informs browsers
Example
A clickable button
<button type="button">Click Me!</button>

Question 15

Q

HTML checkbox

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
Allows selection of 1+ options of limited number of choices
HTML <input> type attribute
a square box that is ticked (checked) when activated
For best accessibility practices, always add <label>
Syntax
<input type="checkbox">
Example
~~~
<input></input>
<label> I have a bike</label><br></br>
<input></input>
<label> I have a car</label><br></br>
<input></input>
<label> I have a boat</label><br></br>
~~~

Question 16

Q

HTML clearInterval

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
Clears a timer set with the setInterval() method
Syntax
clearInterval(intervalId)[Interval ID]
Example
~~~
const myInterval = setInterval(myTimer, 1000);
function myTimer() {
const date = new Date();
document.getElementById(“demo”).innerHTML = date.toLocaleTimeString();
}
function myStopFunction() {
clearInterval(myInterval);
}
~~~
(Displays time every second. Uses clearInterval() to stop time)

Question 17

Q

HTML clearTimeout

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
clears a timer set with setTimeout()
Syntax
clearTimeout(id_of_settimeout)
Example
~~~
const myTimeout = setTimeout(myGreeting, 3000);
function myGreeting() {
document.getElementById(“demo”).innerHTML = “Happy Birthday to You !!”
}
function myStopFunction() {
clearTimeout(myTimeout);
}
~~~
(prevents myGreeting() to execute)

Question 18

Q

HTML clientInformation

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
Properties, methods, & events set inherited from Navigator
Determines if client runs Java applets or if browser’s userAgent contains Microsoft Internet Explorer line
Example
~~~
if (window.clientInformation.javaEnabled()) {
// Java is enabled; applets can run.
}
~~~

Question 19

Q

HTML close

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
closes window opened with open()
Syntax
[item or object].close()
Examples
~~~
document.open();
document.write(“<h1>Hello World</h1>”);
document.write(“<p>Open owerwrites original content.</p>”);
document.close();
~~~
(open a document, write some text to it, and close it)
~~~
function openWin() {
myWindow = window.open(“https://www.w3schools.com”, “_blank”, “width=200, height=100”);
}
function closeWin() {
myWindow.close();
}
~~~
(Open “www.w3schools.com” in a new window, and use close() to close it)

Question 20

Q

HTML closed

Answer

A

HTML Name, Window Object, or Property
JS significant: avoid for variable/function names
closes window opened with open()
Syntax
[item or object].close()
Examples
~~~
document.open();
document.write(“<h1>Hello World</h1>”);
document.write(“<p>Open owerwrites original content.</p>”);
document.close();
~~~
(open a document, write some text to it, and close it)
~~~
function openWin() {
myWindow = window.open(“https://www.w3schools.com”, “_blank”, “width=200, height=100”);
}
function closeWin() {
myWindow.close();
}
~~~
(Open “www.w3schools.com” in a new window, and use close() to close it)

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IES: JS-deck 6 Flashcards

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