Advanced Custom Store with Memoized Invalidation

Snippet

Advanced Custom Store with Memoized Invalidation

Custom Svelte stores can be optimized by overriding the default set/update behavior. By implementing a memoized comparison function, we prevent unnecessary reactive triggers and downstream component re-renders when the data structure hasn't effectively changed, which is critical for complex nested objects.

snippet.js

javascript

import { writable } from 'svelte/store';
 
export function createMemoStore(initialValue, compareFn = (a, b) => JSON.stringify(a) === JSON.stringify(b)) {
  const { subscribe, set, update } = writable(initialValue);
  let currentValue = initialValue;
 
  return {
    subscribe,
    set: (newValue) => {
      if (!compareFn(currentValue, newValue)) {
        currentValue = newValue;
        set(newValue);
      }
    },
    update: (fn) => {
      const newValue = fn(currentValue);
      if (!compareFn(currentValue, newValue)) {
        currentValue = newValue;
        set(newValue);
      }
    }
  };
}

svelte

Breakdown

compareFn = (a, b) => ...

Allows defining custom equality logic, such as deep comparison or ID-based checks.

if (!compareFn(currentValue, newValue))

Short-circuits the store notification if the new value is functionally identical to the current one.

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Advanced Custom Store with Memoized Invalidation

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