Arrays
Arrays are ordered collections of values. You can store strings, numbers, objects, or even other arrays inside them.
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📋 Copy Modern JavaScript Array Methods Snippet
const numbers = [10, 5, 25, 40, 1];
// Immutable Modern Array Methods (ES2023+)
const sorted = numbers.toSorted((a, b) => a - b);
const reversed = numbers.toReversed();
const replaced = numbers.with(0, 99);
// Deduplication
const unique = [...new Set(numbers)];⚠️ 5 Fatal Traps & JavaScript Pitfalls
Trap #1: Array.prototype.sort() Converts to Strings by Default
Calling
[10, 5, 25, 1].sort() produces [1, 10, 25, 5] because JavaScript converts numbers to strings and sorts lexicographically. Always pass a comparator: (a, b) => a - b.Trap #2: Mutating Methods (push, splice, reverse) Altering State
Legacy methods like
sort(), reverse(), and splice() mutate the original array in-place, causing bugs in state-driven UI libraries. Use ES2023 immutable methods: toSorted(), toReversed(), toSpliced().Trap #3: Sparse Arrays Created by new Array(length)
Writing
new Array(5) creates empty slots, NOT undefined values. Iterative methods like map(), forEach(), and filter() completely skip empty slots! Use Array.from({ length: 5 }).Trap #4: delete arr[index] Leaves Empty Holes
Calling
delete arr[1] deletes the value but leaves an empty slot without updating arr.length. Use splice() or toSpliced().Trap #5: Shallow Array Cloning with Nested Objects
[...arr] and arr.slice() copy object references. Modifying an object inside the cloned array mutates the object in the original array. Use structuredClone() for deep copying.💬 Frequently Asked Questions
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