RangeError: invalid array length

The JavaScript exception "Invalid array length" occurs when specifying an array length that is either negative, a floating number or exceeds the maximum supported by the platform (i.e. when creating an Array or ArrayBuffer, or when setting the length property).

The maximum allowed array length depends on the platform, browser and browser version. For Array the maximum length is 232-1. For ArrayBuffer the maximum is 231-1 (2GiB-1) on 32-bit systems. From Firefox version 89 the maximum value of ArrayBuffer is 233 (8GiB) on 64-bit systems.

Note: Array and ArrayBuffer are independent data structures (the implementation of one does not affect the other).

Message

RangeError: invalid array length (V8-based & Firefox)
RangeError: Array buffer allocation failed (V8-based)
RangeError: Array size is not a small enough positive integer. (Safari)

Error type

RangeError

What went wrong?

The error might appear when attempting to produce an Array or ArrayBuffer with an invalid length, which includes:

  • Negative length, via the constructor or setting the length property.
  • Non-integer length, via the constructor or setting the length property. (The ArrayBuffer constructor coerces the length to an integer, but the Array constructor does not.)
  • Exceeding the maximum length supported by the platform. For arrays, the maximum length is 232-1. For ArrayBuffer, the maximum length is 231-1 (2GiB-1) on 32-bit systems, or 233 (8GiB) on 64-bit systems. This can happen via the constructor, setting the length property, or array methods that implicitly set the length property (such as push and concat).

If you are creating an Array using the constructor, you probably want to use the literal notation instead, as the first argument is interpreted as the length of the Array. Otherwise, you might want to clamp the length before setting the length property, or using it as argument of the constructor.

Examples

Invalid cases

js
new Array(Math.pow(2, 40));
new Array(-1);
new ArrayBuffer(Math.pow(2, 32)); // 32-bit system
new ArrayBuffer(-1);

const a = [];
a.length = a.length - 1; // set the length property to -1

const b = new Array(Math.pow(2, 32) - 1);
b.length = b.length + 1; // set the length property to 2^32
b.length = 2.5; // set the length property to a floating-point number

const c = new Array(2.5); // pass a floating-point number

// Concurrent modification that accidentally grows the array infinitely
const arr = [1, 2, 3];
for (const e of arr) {
  arr.push(e * 10);
}

Valid cases

js
[Math.pow(2, 40)]; // [ 1099511627776 ]
[-1]; // [ -1 ]
new ArrayBuffer(Math.pow(2, 31) - 1);
new ArrayBuffer(Math.pow(2, 33)); // 64-bit systems after Firefox 89
new ArrayBuffer(0);

const a = [];
a.length = Math.max(0, a.length - 1);

const b = new Array(Math.pow(2, 32) - 1);
b.length = Math.min(0xffffffff, b.length + 1);
// 0xffffffff is the hexadecimal notation for 2^32 - 1
// which can also be written as (-1 >>> 0)

b.length = 3;

const c = new Array(3);

// Because array methods save the length before iterating, it is safe to grow
// the array during iteration
const arr = [1, 2, 3];
arr.forEach((e) => arr.push(e * 10));

See also