From 7725acc4df08f72e0f74d54a0ee3a8798d6d5828 Mon Sep 17 00:00:00 2001 From: Ilya Kantor Date: Sun, 27 Jun 2021 00:41:46 +0300 Subject: [PATCH] minor fixes --- 1-js/10-error-handling/2-custom-errors/article.md | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/1-js/10-error-handling/2-custom-errors/article.md b/1-js/10-error-handling/2-custom-errors/article.md index ff2e4c52..91828931 100644 --- a/1-js/10-error-handling/2-custom-errors/article.md +++ b/1-js/10-error-handling/2-custom-errors/article.md @@ -21,9 +21,9 @@ Internally, we'll use `JSON.parse`. If it receives malformed `json`, then it thr Our function `readUser(json)` will not only read JSON, but check ("validate") the data. If there are no required fields, or the format is wrong, then that's an error. And that's not a `SyntaxError`, because the data is syntactically correct, but another kind of error. We'll call it `ValidationError` and create a class for it. An error of that kind should also carry the information about the offending field. -Our `ValidationError` class should inherit from the built-in `Error` class. +Our `ValidationError` class should inherit from the `Error` class. -That class is built-in, but here's its approximate code so we can understand what we're extending: +The `Error` class is built-in, but here's its approximate code so we can understand what we're extending: ```js // The "pseudocode" for the built-in Error class defined by JavaScript itself @@ -117,15 +117,15 @@ We could also look at `err.name`, like this: // instead of (err instanceof SyntaxError) } else if (err.name == "SyntaxError") { // (*) // ... -``` +``` The `instanceof` version is much better, because in the future we are going to extend `ValidationError`, make subtypes of it, like `PropertyRequiredError`. And `instanceof` check will continue to work for new inheriting classes. So that's future-proof. -Also it's important that if `catch` meets an unknown error, then it rethrows it in the line `(**)`. The `catch` block only knows how to handle validation and syntax errors, other kinds (due to a typo in the code or other unknown ones) should fall through. +Also it's important that if `catch` meets an unknown error, then it rethrows it in the line `(**)`. The `catch` block only knows how to handle validation and syntax errors, other kinds (caused by a typo in the code or other unknown reasons) should fall through. ## Further inheritance -The `ValidationError` class is very generic. Many things may go wrong. The property may be absent or it may be in a wrong format (like a string value for `age`). Let's make a more concrete class `PropertyRequiredError`, exactly for absent properties. It will carry additional information about the property that's missing. +The `ValidationError` class is very generic. Many things may go wrong. The property may be absent or it may be in a wrong format (like a string value for `age` instead of a number). Let's make a more concrete class `PropertyRequiredError`, exactly for absent properties. It will carry additional information about the property that's missing. ```js run class ValidationError extends Error {