Comprehensive guide to JavaScript control statements covering conditional statements if and switch and loops for while and do-while for controlling program flow in dynamic web applications
This document explains JavaScript control statements, including conditional statements like "if" and "switch", and loops like "for", "while", and "do-while". It demonstrates how these statements enable developers to control program flow and create dynamic web applications.
Control statements in JavaScript allow developers to direct program flow based on conditions and execute code repeatedly using loops. These statements help create dynamic and interactive web applications by enabling efficient data handling and user interaction.
true.1if (condition) {
2// Code to execute if condition is true
3} else {
4// Code to execute if condition is false
5}1const score = 75;
2if (score >= 60) {
3console.log("Passed");
4} else {
5console.log("Failed");
6}1switch (expression) {
2case value1:
3// Code for value1
4break;
5case value2:
6// Code for value2
7break;
8default:
9// Code if no match is found
1const fruit = "Apple";
2switch (fruit) {
3case "Apple":
4console.log("Apples are $2 per pound.");
5break;
6case "Banana":
7console.log("Bananas are $1 per pound.");
8break;
9case "Cherry":
10console.log("Cherries are $3 per pound.");
11break;
12default:
13console.log("Sorry, we are out of stock.");
14}Loops allow repeated execution of a code block.
1for (initialization; condition; increment) {
2// Code to execute
3}1for (let i = 0; i <= 3; i++) {
2console.log(`Number: ${i}`);
3}
4//OR
5const colors = ["red", "green", "blue"];
6for (let i = 0; i < colors.length; i++) {
7console.log(colors[i]);
8}true.1while (condition) {
2// Code to execute
3} 1let countdown = 5;
2while (countdown > 0) {
3 console.log(`Countdown: ${countdown}`);
4 countdown--;
5}
6//OR
7let n = 0;
8let max = 3;
9while (n < max) {
10 console.log(`Value is ${n}`);
11 n++;
12}
13
true.1do {
2// Code to execute
3} while (condition); 1let i = 0;
2do {
3console.log(`DoWhile iteration: ${i}`);
4i++;
5} while (i < 3);
6//OR
7let passwordCorrect = false;
8do {
9console.log("Attempt login");
10// Simulate login
11passwordCorrect = true;
12} while (!passwordCorrect);Control statements like if, switch, for and while and do while are essential for controlling the programme flow. Loops and control statements provide a foundation for more complex programming tasks, by understanding and using these control statements effectively, developers can create dynamic and interactive web applications that meet the needs of their users. , allowing developers to create more sophisticated and dynamic applications.
if statement is important because it allows developers to execute specific blocks of code based on conditions, enabling decision-making in programs.for loop is generally better for iterating over arrays because it provides a concise syntax for initializing, checking conditions, and incrementing in a single line.switch statement can replace multiple if-else conditions when comparing a single expression against multiple values, making the code more readable and organized.while loop checks the condition before executing the code block, while the do-while loop executes the code block at least once before checking the condition.for loop’s condition is never met, the loop will not execute its code block, and the program will continue with the next statement after the loop.switch statement is used to match an expression’s value against multiple case labels, executing the corresponding code block for the first matching case.do-while loop should be used when you need to ensure the code block executes at least once, regardless of the condition.for loop is not suitable for iterating over objects. Instead, you can use for...in or Object.keys() with a for loop to iterate over object properties.if-else statement improves decision-making by allowing developers to execute different blocks of code based on whether a condition evaluates to true or false.break statement is essential in a switch block to prevent the execution from falling through to subsequent cases after a match is found.for loop is used to execute a block of code a specific number of times, making it ideal for tasks like iterating over arrays or performing repetitive operations.do-while loop ensures code execution at least once by evaluating the condition after the code block has been executed.