Switch statement in Javascript - Step-by-Step Execution

Concept Flow - Switch statement

Start

↓

Evaluate expression

↓

Compare with case 1?

No→Compare with case 2?

↓

Execute case 1

↓

Break?

No→Continue to next case

Yes↓

Exit switch

The switch statement evaluates an expression and compares it to each case value. When a match is found, it executes that case's code until a break is encountered or the switch ends.

Execution Sample

Javascript

let day = 3;
switch(day) {
  case 1:
    console.log('Monday');
    break;
  case 3:
    console.log('Wednesday');
    break;
  default:
    console.log('Other day');
}

This code checks the value of 'day' and prints the matching weekday name or 'Other day' if no match.

Execution Table

Step	Expression Value	Case Compared	Match?	Action	Output
1	3	1	No	Check next case
2	3	3	Yes	Execute case 3 block	Wednesday
3				Break encountered, exit switch

💡 Break statement stops execution after matching case 3.

Variable Tracker

Variable	Start	After Step 1	After Step 2	Final
day	3	3	3	3

Key Moments - 2 Insights

Why does the switch stop after printing 'Wednesday'?

Because the break statement at the end of case 3 stops the switch from continuing to other cases, as shown in execution_table step 3.

What happens if we remove the break in case 3?

Without break, the switch would continue executing the next cases until it finds a break or ends, causing multiple outputs. This is called 'fall-through'.

Visual Quiz - 3 Questions

Look at the execution table, what is the output at step 2?

A Other day

B Monday

C Wednesday

D No output

💡 Hint

Check the 'Output' column at step 2 in the execution_table.

At which step does the switch statement stop executing?

A Step 3

B Step 1

C Step 2

D It never stops

💡 Hint

Look at the 'Action' column in execution_table where break is encountered.

If the variable 'day' was 2, what would be the output?

A Monday

B Other day

C Wednesday

D No output

💡 Hint

Since 2 matches no case, the default case runs as per the code in execution_sample.

Concept Snapshot

switch(expression) {
  case value1:
    // code
    break;
  case value2:
    // code
    break;
  default:
    // code
}

- Compares expression to cases
- Executes matching case
- Use break to stop fall-through
- Default runs if no match

Full Transcript

The switch statement starts by evaluating the expression. It then compares this value to each case in order. If a case matches, the code inside that case runs. The break statement stops the switch from running other cases. If no case matches, the default case runs. In the example, day equals 3, so it matches case 3 and prints 'Wednesday'. The break stops further execution. If break was missing, the switch would continue running the next cases, which can cause multiple outputs. This is called fall-through. Understanding where and why break is used helps control the flow inside switch statements.