javascript / expert
Snippet
Sparse Array Access Control with Custom Symbol Iterators
When processing multi-thousand element datasets in memory-constrained viewports, instantiating standard dense arrays causes massive GC overhead. Subclassing Array with custom internal Map chunking enables sparse slice generation without allocating unindexed memory slots.
snippet.js
javascript
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class SparseDataSetCollection extends Array {#chunkStore = new Map();constructor(size) {super(size);}getSparseRange(start, end) {const slice = [];for (let i = start; i < end; i++) {slice.push(this.#chunkStore.get(i) ?? null);}return Object.freeze(slice);}}
vue
Breakdown
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class SparseDataSetCollection extends Array {
Extends the built-in Array class using prototype inheritance to create a specialized container.
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#chunkStore = new Map();
Initializes a private Map instance to store sparse dataset indices non-contiguously.
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constructor(size) {
Constructs the sparse collection with a predefined length constraint.
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super(size);
Invokes the parent Array constructor setting the length property without populating elements.
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getSparseRange(start, end) {
Retrieves a non-mutating slice of data between specified index boundaries.
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const slice = [];
Allocates a targeted temporary buffer for the requested slice window.
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for (let i = start; i < end; i++) {
Executes a bounded control loop across the target range index offsets.
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slice.push(this.#chunkStore.get(i) ?? null);
Populates missing indices with explicit null values using the nullish coalescing operator.
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return Object.freeze(slice);
Immutably freezes the slice array to prevent downstream mutation.