Shallow Copy
let a
let b = a
↓ ↓
[1, 2, 3, 4]
same memory
Deep Copy
let a
let b = [...a]
↓ ↓
[1, 2, 3, 4]
[1, 2, 3, 4]
different memory
Shallow Copy
The shallow copy of an object will refer to the same memory as the original array.
let a = [1,2,3,4] // Memory Address : 10225
let b = a; // Memory Address : 10225 (same)
b.push(5) // Changes in b
console.log(a) // [1,2,3,4,5]Deep Copy
The memory reference will not be the same when copying using a deep copy method. Using the Spread Operator or map:
// Using map
let a = [1,2,3,4]
let b = a.map((e) => e);
b.push(5)
console.log(a) // [1,2,3,4]// Using spread operator
let a = [1,2,3,4]
let b = [...a];
b.push(5)
console.log(a) // [1,2,3,4]