Try–catch block in Javascript - Step-by-Step Execution

Concept Flow - Try–catch block

Start

↓

Try block runs

↓

Error?

No→Try block ends normally

|Yes↓

Catch block runs

↓

Continue after catch

↓

End

The program tries to run code inside the try block. If an error happens, it jumps to the catch block to handle it, then continues.

Execution Sample

Javascript

try {
  let result = 10 / 0;
  console.log('Result:', result);
} catch (error) {
  console.log('Error caught:', error.message);
}

This code tries to divide 10 by 0 and print the result. If an error occurs, it catches and prints the error message.

Execution Table

Step	Action	Evaluation	Result
1	Enter try block	No error yet	Continue
2	Calculate 10 / 0	Division by zero in JS returns Infinity	result = Infinity
3	console.log('Result:', result)	Prints 'Result: Infinity'	Output: Result: Infinity
4	Try block ends	No error thrown	Skip catch block
5	Program continues after try-catch	Normal flow	End

💡 Try block completed without error, so catch block is skipped.

Variable Tracker

Variable	Start	After Step 2	Final
result	undefined	Infinity	Infinity
error	undefined	undefined	undefined

Key Moments - 2 Insights

Why doesn't the catch block run when dividing by zero?

In JavaScript, dividing by zero does not throw an error; it returns Infinity. So the try block finishes normally and the catch block is skipped, as shown in execution_table step 4.

What happens if an error is thrown inside the try block?

If an error occurs, execution immediately jumps to the catch block to handle it. This is not shown here but would appear as a jump from try to catch in the flow.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'result' after step 2?

A Infinity

B 0

C Error

D undefined

💡 Hint

Check the 'Evaluation' and 'Result' columns in row 2 of the execution_table.

At which step does the catch block run in this example?

A Step 3

B Step 4

C Never

D Step 5

💡 Hint

Look at the 'Result' column in step 4; it says 'Skip catch block'.

If the code inside try threw an error, what would happen next?

A The program would crash immediately

B The catch block would run to handle the error

C The try block would continue running

D Nothing changes, catch block is ignored

💡 Hint

Refer to the concept_flow where error leads to catch block execution.

Concept Snapshot

try {
  // code that might fail
} catch (error) {
  // code to handle error
}

- Runs try block code
- If error occurs, jumps to catch
- catch receives error object
- After catch, program continues normally

Full Transcript

A try-catch block lets your program try to run code that might cause an error. If an error happens, the program jumps to the catch block to handle it without crashing. In JavaScript, some things like dividing by zero do not cause errors but return special values like Infinity, so catch does not run. The try block runs first, and if no error occurs, the catch block is skipped. If an error happens, the catch block runs with the error details. After catch, the program continues normally.