Control flow refers to the order in which instructions are executed in a program. It determines the path the program takes based on conditions and decisions.
Default Control Flow Order:
In JavaScript, code is executed sequentially from top to bottom by default. This means that statements are processed in the order they appear in the code.
Control Structures and Conditionals:
Control structures like if statements, switch statements, and loops enable you to make decisions and control the flow of your program based on certain conditions.
if Statement:
The 'if' statement is used to execute a block of code if a specified condition is 'true'.
Example:
let temperature = 28;
if (temperature > 30) {
console.log("It's a hot day.");
}
else Statement:
The 'else' statement is used alongside an 'if' statement. It executes a block of code when the condition of the 'if' statement is 'false'.
Example:
let weather = "rainy";
if (weather === "sunny") {
console.log("It's sunny!");
} else {
console.log("It's not sunny.");
}
switch Statement:
The 'switch' statement allows you to evaluate an expression against multiple possible case values and execute corresponding code blocks.
Example:
let day = "Monday";
switch (day) {
case "Monday":
console.log("Start of the week");
break;
case "Friday":
console.log("End of the week");
break;
default:
console.log("Somewhere in between");
}
Truthy and Falsy Values:
In JavaScript, values that are considered "truthy" evaluate to 'true' in boolean contexts, while "falsy" values evaluate to 'false'.
Example:
let username = ""; // Falsy
if (username) {
console.log("Username provided.");
} else {
console.log("Username not provided.");
}
else if Clause:
The 'else if' clause is used to specify an additional condition to check if the preceding 'if' or 'else if' conditions are false.
Example:
let grade = 85;
if (grade >= 90) {
console.log("A");
} else if (grade >= 80) {
console.log("B");
} else if (grade >= 70) {
console.log("C");
} else {
console.log("F");
}