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Barrios Freddy
Barrios Freddy

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How to empty an array in JavaScript

#javascript #node #tutorial #tricks

The simple way to empty an array in JavaScript is through assigning 0 to the property length of the array affected. For Example

let numbers = [1,3,5,7,9];

numbers.length = 0;

console.log(numbers);
// []
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This is possible because the length property is read/write property in an array. Therefore, you can assign zero and the array will be clear.

Top comments (4)

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bttodd11 profile image
Brian Todd •

Wouldnt it be the same assigning to an empty array?
let numbers = [] ;

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jonrandy profile image
Jon Randy 🎖️ • • Edited

Nope. If you had another reference to the original array, the original array would still remain at the other reference - you have done nothing to the original array.

Compare:

let numbers = [1, 3, 5, 7, 9];
let numbers_b = numbers; // another reference to same array
numbers.length = 0;

console.log(numbers_b);
// []
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And:

let numbers = [1, 3, 5, 7, 9];
let numbers_b = numbers; // another reference to same array
numbers = [];

console.log(numbers_b);
// [1, 3, 5, 7, 9]
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Assigning to an empty array does exactly that - assigns a new array to the variable. Entirely different to emptying an existing array. 'Emptying' an array by simply overwriting it with a new empty array could easily cause unexpected problems.

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jackydev profile image
JacKyDev •

I think Not..
Its the Same result but the author used the existing Array in context and you create an complete new Array for context

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bias profile image
Tobias Nickel •

yes, any just by doing so, the author introduce a implicit dependencies between components. Using the same array all over the and somewhere it get emptied will cause some nice side effects.

This will give you some fun debugging session.

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