try / catch / finally

                try { } catch (error) { } finally { }
              

Purpose

try runs a block of code; if anything inside it throws, catch runs instead of letting the error crash the program (or propagate to the caller). finally, if present, always runs afterward — whether or not an error occurred, and even if try or catch returns early.

Syntax

function parseConfig(json) {
  try {
    return JSON.parse(json);
  } catch (error) {
    console.error('Invalid config JSON:', error.message);
    return {};
  } finally {
    console.log('Parse attempt finished.');
  }
}

Behavior notes

• catch (error) receives the thrown value — conventionally an Error instance, with .message and .name properties, though technically any value can be thrown.
• catch can be omitted if only finally is needed (try { } finally { }) — useful for cleanup that must run whether or not an error occurred, without handling the error at that level.
• Only synchronous errors thrown directly inside the try block are caught. A callback scheduled from inside try (a setTimeout, for instance) that throws later is not caught by that try — asynchronous error handling is covered later in this tier.
• A return inside try or catch still lets finally run first before the function actually returns.

Common mistakes

• Wrapping too much code in one try block, making it unclear which line could actually throw and obscuring what specifically is being guarded against.
• Catching an error and silently doing nothing with it (catch (e) {}) — this hides real bugs. At minimum, log what was caught.
• Expecting try/catch to catch an error thrown inside an asynchronous callback scheduled from within the try block.

Runtime notes

Core ECMAScript statement, identical behavior in every browser and Node version.