debugging

Author: dummdidumm

apps/svelte.dev/content/docs/svelte/03-runes/01-state.md

@@ -63,6 +63,8 @@ Objects and arrays are made deeply reactive by wrapping them with [`Proxies`](ht
 <button onclick={() => entries[1].text = 'baz'}>change second entry text</button>
 ```
 
+> Only POJOs (plain of JavaScript objects) are made deeply reactive. Reactivity will stop at class boundaries and leave those alone
+
 ## `$state.frozen`
 
 State declared with `$state.frozen` cannot be mutated; it can only be _reassigned_. In other words, rather than assigning to a property of an object, or using an array method like `push`, replace the object or array altogether if you'd like to update it:

apps/svelte.dev/content/docs/svelte/05-misc/01-debugging.md

@@ -4,3 +4,91 @@ title: Debugging
 
 - `@debug`
 - `$inspect`
+
+Svelte provides two built-in ways to debug your application.
+
+## `$inspect`
+
+The `$inspect` rune is roughly equivalent to `console.log`, with the exception that it will re-run whenever its
+argument changes. `$inspect` tracks reactive state deeply, meaning that updating something inside an object
+or array using fine-grained reactivity will cause it to re-fire. ([Demo:](/#H4sIAAAAAAAACkWQ0YqDQAxFfyUMhSotdZ-tCvu431AXtGOqQ2NmmMm0LOK_r7Utfby5JzeXTOpiCIPKT5PidkSVq2_n1F7Jn3uIcEMSXHSw0evHpAjaGydVzbUQCmgbWaCETZBWMPlKj29nxBDaHj_edkAiu12JhdkYDg61JGvE_s2nR8gyuBuiJZuDJTyQ7eE-IEOzog1YD80Lb0APLfdYc5F9qnFxjiKWwbImo6_llKRQVs-2u91c_bD2OCJLkT3JZasw7KLA2XCX31qKWE6vIzNk1fKE0XbmYrBTufiI8-_8D2cUWBA_AQAA))
+
+```svelte
+<script>
+	let count = $state(0);
+	let message = $state('hello');
+
+	$inspect(count, message); // will console.log when `count` or `message` change
+</script>
+
+<button onclick={() => count++}>Increment</button>
+<input bind:value={message} />
+```
+
+`$inspect` returns a property `with`, which you can invoke with a callback, which will then be invoked instead of `console.log`. The first argument to the callback is either `"init"` or `"update"`, all following arguments are the values passed to `$inspect`. [Demo:](/#H4sIAAAAAAAACkVQ24qDMBD9lSEUqlTqPlsj7ON-w7pQG8c2VCchmVSK-O-bKMs-DefKYRYx6BG9qL4XQd2EohKf1opC8Nsm4F84MkbsTXAqMbVXTltuWmp5RAZlAjFIOHjuGLOP_BKVqB00eYuKs82Qn2fNjyxLtcWeyUE2sCRry3qATQIpJRyD7WPVMf9TW-7xFu53dBcoSzAOrsqQNyOe2XUKr0Xi5kcMvdDB2wSYO-I9vKazplV1-T-d6ltgNgSG1KjVUy7ZtmdbdjqtzRcphxMS1-XubOITJtPrQWMvKnYB15_1F7KKadA_AQAA)
+
+```svelte
+<script>
+	let count = $state(0);
+
+	$inspect(count).with((type, count) => {
+		if (type === 'update') {
+			debugger; // or `console.trace`, or whatever you want
+		}
+	});
+</script>
+
+<button onclick={() => count++}>Increment</button>
+```
+
+A convenient way to find the origin of some change is to pass `console.trace` to `with`:
+
+```js
+// @errors: 2304
+$inspect(stuff).with(console.trace);
+```
+
+> `$inspect` only works during development. In a production build it becomes a noop.
+
+## @debug
+
+```svelte
+<!--- copy: false --->
+{@debug}
+```
+
+```svelte
+<!--- copy: false --->
+{@debug var1, var2, ..., varN}
+```
+
+The `{@debug ...}` tag offers an alternative to `console.log(...)`. It logs the values of specific variables whenever they change, and pauses code execution if you have devtools open.
+
+```svelte
+<script>
+	let user = {
+		firstname: 'Ada',
+		lastname: 'Lovelace'
+	};
+</script>
+
+{@debug user}
+
+<h1>Hello {user.firstname}!</h1>
+```
+
+`{@debug ...}` accepts a comma-separated list of variable names (not arbitrary expressions).
+
+```svelte
+<!-- Compiles -->
+{@debug user}
+{@debug user1, user2, user3}
+
+<!-- WON'T compile -->
+{@debug user.firstname}
+{@debug myArray[0]}
+{@debug !isReady}
+{@debug typeof user === 'object'}
+```
+
+The `{@debug}` tag without any arguments will insert a `debugger` statement that gets triggered when _any_ state changes, as opposed to the specified variables.