How do I empty an array in JavaScript?

To empty an array in JavaScript, you can use one of the following methods, depending on your needs:

1. Set length = 0 (Fastest, Mutates Original Array)

Resets the array length to 0, clearing all elements.
Use this if other references to the array should also reflect the change.

let arr = [1, 2, 3];
arr.length = 0; // arr becomes []

2. Reassign to a New Empty Array

Creates a new empty array and reassigns the variable.
Use this if there are no other references to the original array.

let arr = [1, 2, 3];
arr = []; // arr now points to a new empty array

3. Use splice() (Mutates Original Array)

Removes all elements from the array using splice.

let arr = [1, 2, 3];
arr.splice(0, arr.length); // arr becomes []

4. Loop and Remove Elements (Not Recommended)

Inefficient for large arrays, but works:

let arr = [1, 2, 3];
while (arr.length > 0) {
  arr.pop();
}

Key Differences

Method	Mutates Original Array	Handles Other References?	Performance
arr.length = 0	✅ Yes	✅ Yes (updates all refs)	Fastest
Reassignment (= [])	❌ No (new array)	❌ No (old refs remain)	Fast
splice()	✅ Yes	✅ Yes	Fast
Loop (pop/shift)	✅ Yes	✅ Yes	Slow

Example Scenarios

1. If the array is declared with const:

   const arr = [1, 2, 3];
   arr.length = 0; // ✅ Works (mutates the array)
   // arr = [] ❌ Throws an error (reassignment not allowed)

2. Other references to the array:

   let arr = [1, 2, 3];
   let arr2 = arr; // arr2 references the same array

   arr.length = 0; // Both arr and arr2 become []

Which Method Should You Use?

• Best for most cases: arr.length = 0 (efficient and updates all references).
• Avoid reassignment (= []) if other parts of your code reference the original array.
• Avoid loops unless you need incremental processing.

Let me know if you need further clarification!