Validation and error handling
Protect the ledger from bad input
Real users mistype, paste spaces, and leave fields empty. Production code treats that as expected behavior. A validation function either returns a clean transaction or throws a precise error. The submit handler catches it and shows a useful message.
Never silently turn invalid money into zero. Invalid is not empty, and empty is not zero.
操作说明
Create createTransaction(description, amount) and trim the description.
提示： const cleanDescription = description.trim();
这段代码写在哪里？
// Build createTransaction(description, amount), then use try/catch on submit.写在第 5 行——在那条注释下方，接在你已经写好的代码后面。
Reject a short description and non-positive or non-finite amount.
Wrap transaction creation in try/catch.
Show the error message in #form-error.
你的代码
描述你想为这一步构建的内容，我来编写代码——然后点击「应用」把它放进你的编辑器。 本步骤：Create createTransaction(description, amount) and trim the description.