Reactivity /
a. Basics b. Adding data c. Dynamic attributes d. Styling e. Nested components f. Making an app a. Assignments b. Declarations c. Statements d. Updating arrays and objects a. Declaring props b. Default values c. Spread props a. If blocks b. Else blocks c. Else-if blocks d. Each blocks e. Keyed each blocks f. Await blocks a. DOM events b. Inline handlers c. Event modifiers d. Component events e. Event forwarding f. DOM event forwarding a. Text inputs b. Numeric inputs c. Checkbox inputs d. Group inputs e. Textarea inputs f. Select bindings g. Select multiple h. Contenteditable bindings i. Each block bindings j. Media elements k. Dimensions l. This m. Component bindings n. Binding to component instances a. onMount b. onDestroy c. beforeUpdate and afterUpdate d. tick a. Writable stores b. Auto-subscriptions c. Readable stores d. Derived stores e. Custom stores f. Store bindings a. Tweened b. Spring a. The transition directive b. Adding parameters c. In and out d. Custom CSS transitions e. Custom JS transitions f. Transition events g. Local transitions h. Deferred transitions i. Key blocks a. The animate directive a. The use directive b. Adding parameters a. The class directive b. Shorthand class directive c. Inline styles d. The style directive a. Slots b. Slot fallbacks c. Named slots d. Checking for slot content e. Slot props a. setContext and getContext a. <svelte:self> b. <svelte:component> c. <svelte:element> d. <svelte:window> e. <svelte:window> bindings f. <svelte:document> g. <svelte:body> h. <svelte:head> i. <svelte:options> j. <svelte:fragment> a. Sharing code b. Exports a. The @debug tag b. HTML tags a. Congratulations!
At the heart of Svelte is a powerful system of reactivity for keeping the DOM in sync with your application state — for example, in response to an event.
To demonstrate it, we first need to wire up an event handler. Replace line 9 with this:
< button on : click = {incrementCount}> Inside the incrementCount function, all we need to do is change the value of count:
function incrementCount () { count += 1 ; } Svelte 'instruments' this assignment with some code that tells it the DOM will need to be updated.
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