Creating and Copying Arrays

2.1 Creating and Copying Arrays

Shallow Copying and Reference Behavior

Explanation
The spread operator creates a new array by expanding elements of an existing array. This new array has a different reference in memory. Primitive values are copied independently, so changes do not affect the original array. Nested objects or arrays remain shared by reference. The original array is never mutated during this process.

Code / Tabular Examples

const original = [1, 2, 3];

const copy = [...original];

copy.push(4);

Example
Direct assignment of arrays shares the same reference.
Using spread creates a new independent array.
Changes made to the copied array do not affect the original.
This prevents unexpected side effects in programs.
It is widely used in immutable programming patterns.

Use Cases

• Safely duplicating arrays
  
• Avoiding reference-based bugs
  
• Preserving original datasets
  
• Working with immutable state

2.2 Merging and Expanding Arrays

Combining Multiple Arrays Safely

Explanation
The spread operator allows multiple arrays to be merged into a single array. Each array is expanded in sequence inside a new array literal. No source array is modified during the merge. Additional elements can be inserted at any position. The result is a clean and predictable combined array.

Code / Tabular Examples

const a = [1, 2];

const b = [3, 4];

const merged = [...a, ...b, 5];

Example
Traditional merging often requires chained method calls.
Spread merges arrays in a single readable expression.
The order of elements is preserved exactly.
Extra values can be added during merging.
This improves clarity and reduces code complexity.

Use Cases

• Combining data from different sources
  
• Appending elements while merging
  
• Building option or configuration lists
  
• Simplifying array construction