Control flow statements allow your program to make decisions and execute different blocks of code based on certain conditions.
4.1 if, else if, else statements
The if statement executes a block of code if a specified condition is true. You can extend it with else if for multiple conditions and else for a default case.
-
Syntax
if (condition1) { // Code to execute if condition1 is true } else if (condition2) { // Code to execute if condition1 is false AND condition2 is true } else { // Code to execute if all conditions are false } -
Example
let temperature = 25; if (temperature > 30) { console.log("It's hot!"); } else if (temperature > 20) { console.log("It's warm."); } else { console.log("It's cool."); } // Output: It's warm.
4.2 switch statements
The switch statement is an alternative to long if-else if chains when you're checking a single variable against multiple possible values.
-
Syntax
switch (expression) { case value1: // Code if expression matches value1 break; // Important: exits the switch block case value2: // Code if expression matches value2 break; default: // Code if no match is found } -
Example
let day = "Monday"; switch (day) { case "Monday": console.log("Start of the week."); break; case "Friday": console.log("Almost weekend!"); break; default: console.log("Mid-week day."); } // Output: Start of the week.The
breakkeyword is crucial to prevent "fall-through" where code from subsequentcaseblocks would also execute.
4.3 Conditional (Ternary) Operator for Decisions
As seen in Chapter 3, the ternary operator (condition ? valueIfTrue : valueIfFalse;) is a concise way to make simple conditional assignments or expressions.
-
Example
let age = 16; let canVote = (age >= 18) ? "Yes" : "No"; console.log(canVote); // Output: No
Join the conversation! Your thoughts help the community grow.