🪴 TJ's Notes 1.0

Web Programming Lecture 13

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Web Programming - Lecture 13

JavaScript

For some reason prebuilt functions are called methods here

1. Comparison Operators

  • Equality (==): Compares two values for equality, after converting both values to a common type.
  • Strict Equality (===): Compares two values for equality without converting their types.
  • Inequality (!=): Compares two values for inequality, after converting both values to a common type.
  • Strict Inequality (!==): Compares two values for inequality without converting their types.
  • Greater Than (>): Checks if the left value is greater than the right value.
  • Greater Than or Equal To (>=): Checks if the left value is greater than or equal to the right value.
  • Less Than (<): Checks if the left value is less than the right value.
  • Less Than or Equal To (<=): Checks if the left value is less than or equal to the right value.

2. Type of Function

  • typeof Operator: Returns the type of the variable or expression. Common types include:
    • "string"
    • "number"
    • "boolean"
    • "undefined"
    • "object"
    • "function"
  • Example:
  console.log(typeof 42);           // "number"
  console.log(typeof "Hello");      // "string"
  console.log(typeof true);         // "boolean"
  console.log(typeof undefined);    // "undefined"
  console.log(typeof {key: "value"}); // "object"
  console.log(typeof function(){}); // "function"

3. Number() Method

  • Purpose: Converts a value to the most logical number type variable.
  • Behavior:
    • Converts strings that represent numbers to actual numbers.
    • Converts false to 0 and true to 1.
    • If the value can’t be converted to a number, it returns NaN.
  • Example:
  console.log(Number("42"));      // 42
  console.log(Number("42.5"));    // 42.5
  console.log(Number(true));      // 1
  console.log(Number(false));     // 0
  console.log(Number("Hello"));   // NaN

4. parseFloat()

  • Purpose: Converts the closest

5. parseInt()

  • Purpose: Converts to the closest integer value that is a whole number
  • Behaviour:
    • Converts any given float number to the nearest whole integer
    • Converts Binary to decimal if base is given. ( 2nd parameter )
console.log(parseInt("42"));       // 42
console.log(parseInt("42.7"));     // 42
console.log(parseInt("42px"));     // 42
console.log(parseInt("1010", 2));  // 10 (binary to decimal)
console.log(parseInt("Hello"));    // NaN

6. getElementByID()

  • Syntax document.getElementByID(id)
  • The function basically takes the id as a parameter and find that class in the html page and then select it.
  • This is conventionally stored in a variable for further use of its subclass. Refer getElementByID

Assignment 4

  • WAP to identify whether a visited user is eligible for e-voting. Criteria are as follows.
  • Visited user should be more than 25 years
  • If he is male print hello Mr.(name) else print Miss(Name)
  • Else you are not entitled to visit this page

Solution

<!DOCTYPE html>
 
<html lang="en">
 
<head>
 
<meta charset="UTF-8">
 
<meta name="viewport" content="width=device-width, initial-scale=1.0">
 
<title>My Website</title>
 
</head>
 
<body>
 
<h1>Enter the details as the prompt says</h1>
 
<script src="script.js"></script>
 
</body>
 
</html>
var gender = prompt("Enter your gender: ", "Gender").toLowerCase();
 
var age = prompt("Enter your age: ", "Age");
 
var name = prompt("Enter your name: ", "Name");
 
  
 
if (age < 25) {
 
document.write("Hello, " + name + "! You are not entitled to visit this page");
 
} else {
 
if (gender == "male") {
 
document.write("Hello, Mr. " + name + "! You are entitled to visit this page");
 
} else if (gender == "female") {
 
document.write("Hello, Mrs. " + name + "! You are entitled to visit this page");
 
} else {
 
document.write("Hello, You are not entitled to visit this page");
 
}
 
}

Assignment 5

  • Write a program to find the average of marks of n Subjects by using js

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