JavaScript Control Flow Statements (original) (raw)

Last Updated : 07 Jun, 2025

Control flow statements in JavaScript control the order in which code is executed. These statements allow you to make decisions, repeat tasks, and jump between parts of a program based on specific conditions.

JavaScript if Statement

The if statement executes a block of code only if a specified condition is true.

JavaScript `

const age = 18; if (age >= 18) { console.log("You are an adult."); }

`

• Checks if age is greater than or equal to 18.
• Logs "You are an adult." if the condition is true.

JavaScript if...else Statement

The if...else statement provides an alternate block of code to execute if the condition is false.

JavaScript `

const score = 40; if (score >= 50) { console.log("You passed."); } else { console.log("You failed."); }

`

• It will log "You passed." if the score is 50 or more.
• Otherwise, logs "You failed."

JavaScript if...else if...else Statement

The if...else if...else statement is used when you want to handle multiple conditions.

JavaScript `

const temp = 25; if (temp > 30) { console.log("It's hot."); } else if (temp >= 20) { console.log("It's warm."); } else { console.log("It's cold."); }

`

• Checks if the temperature is greater than 30, logs "It's hot."
• If not, checks if it's between 20 and 30, logs "It's warm."
• Otherwise, logs "It's cold."

JavaScript switch Statement

The switch statement evaluates an expression and executes a block of code based on matching cases. It provides an alternative to long if-else chain.

JavaScript `

const day = "Monday"; switch (day) { case "Monday": console.log("Start of the week."); break; case "Friday": console.log("End of the workweek."); break; default: console.log("It's a regular day."); }

`

• Checks the value of day and matches it to a case.
• Logs "Start of the week." if day is "Monday".
• Logs "End of the workweek." if day is "Friday".
• Logs "It's a regular day." if no cases match.

JavaScript Ternary Operator or Conditional Operator:

In some programming languages, a ternary operator is used to assign a value to a variable based on a condition.

JavaScript `

let a = 10; console.log(a === 5 ? "a is equal to 5" : "a is not equal to 5");

`

**Output

a is not equal to 5

• **Variable Declaration: let a = 10; assigns 10 to variable a.
• **Ternary Operator: a === 5 ? "a is equal to 5" : "a is not equal to 5"; checks if a is strictly equal to 5.
  • If true, it returns "a is equal to 5".
  • If false, it returns "a is not equal to 5".

Uses of Control Flow Statements

Control flow statements are backbone in programming for

• **Decision-Making: To execute specific blocks of code based on conditions (e.g., if, if...else).
• **Branching: To exit loops or skip iterations (break, continue).
• **Looping: To repeat tasks (for, while, do...while).
• **Switching: To handle multiple conditions effectively (switch).