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Answer (EN)

## Short answer

The `catch` block **runs only**
when an **error (exception) occurs** in the `try` block,
either thrown manually (`throw`) or automatically (for example, `ReferenceError`, `TypeError`, and so on).

If the code inside `try` runs without errors, `catch` **is skipped**.

---

## Step-by-step mechanism

1. The code inside `try { ... }` starts running line by line.
2. If it **doesn't raise any errors**, `catch` is not called.
3. If an **error occurs** inside `try`, execution of `try`
**stops immediately**, and control moves to `catch`.
4. Inside `catch(error)` you have access to the **error object**, which you can handle or log.

---

## Example 1. No error -> `catch` doesn't run

```javascript
try {
  console.log("Everything is working great!");
} catch (error) {
  console.log("Caught an error:", error.message);
}

console.log("Continuing execution...");
```

Output:

```javascript
Everything is working great!
Continuing execution...
```

> Since there was no error inside `try`, `catch` doesn't run.

---

## Example 2. There is an error -> `catch` runs

```javascript
try {
  console.log("Start");
  throw new Error("An error occurred!");
  console.log("This code will not run");
} catch (error) {
  console.log("Caught:", error.message);
}
```

Output:

```javascript
Start
Caught: An error occurred!
```

> After `throw`, execution of `try` stops,
> and control passes to `catch`.

---

## Example 3. An automatic error

```javascript
try {
  console.log(a); // ReferenceError: a is not defined
} catch (error) {
  console.log("Caught:", error.name); // ReferenceError
}
```

> Here `catch` runs because JS automatically threw an exception when accessing an undefined variable.

---

## Example 4. Several lines - an error "cuts off" try

```javascript
try {
  console.log("1");
  JSON.parse("not valid JSON"); // error here
  console.log("2"); // will not run
} catch (error) {
  console.log("Caught:", error.message);
}
console.log("3");
```

Output:

```javascript
1
Caught: Unexpected token n in JSON at position 0
3
```

> As soon as the error happens, `try` stops, and `catch` runs.

---

## Example 5. An error outside `try` - `catch` doesn't run

```javascript
try {
  console.log("Everything is fine inside try");
} catch (error) {
  console.log("Caught an error:", error.message);
}

throw new Error("Error outside try!"); // won't be caught
```

The error won't be caught, because it happened **outside** the `try` block.

---

## Example 6. An error inside asynchronous code

> Important: `try...catch` **does not catch errors inside callbacks and promises**
> unless you use `await` or `.catch()`.

```javascript
try {
  setTimeout(() => {
    throw new Error("Error in the callback"); // won't be caught
  }, 1000);
} catch (e) {
  console.log("Caught:", e.message);
}
```

> To catch errors from promises, you need to use `async/await` or `.catch()`:

Correct:

```javascript
async function run() {
  try {
    await Promise.reject(new Error("Error in the promise"));
  } catch (e) {
    console.log("Caught:", e.message);
  }
}
run();
```

---

## Example 7. If there are several errors, the first one is caught

```javascript
try {
  throw new Error("Error 1");
  throw new Error("Error 2"); // will not run
} catch (err) {
  console.log("Caught:", err.message);
}
```

Output:

```javascript
Caught: Error 1
```

---

## Summary

| Situation | Does catch run? | Reason |
|---|---|---|
| No errors in `try` | No | The code ran normally |
| `throw` in `try` | Yes | The exception was handled |
| JS itself threw an error (ReferenceError, etc.) | Yes | Automatic error |
| Error outside `try` | No | Not within the handled scope |
| Error in a callback/Promise without await | No | Asynchronous code outside try |

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