W3cubDocs

Errors: Invalid array length

The JavaScript exception "Invalid array length" occurs when creating an Array or an ArrayBuffer which has a length which is either negative or larger or equal to 2³², or when setting the Array.length property to a value which is either negative or larger or equal to 2³².

Message

RangeError: Array length must be a finite positive integer (Edge)
RangeError: invalid array length (Firefox)
RangeError: Invalid array length (Chrome)
RangeError: Invalid array buffer length (Chrome)

Error type

RangeError

What went wrong?

An invalid array length might appear in these situations:

When creating an Array or an ArrayBuffer which has a length which is either negative or larger or equal to 2³², or
when setting the Array.length property to a value which is either negative or larger or equal to 2³².

Why are Array and ArrayBuffer length limited? The length property of an Array or an ArrayBuffer is represented with an unsigned 32-bit integer, that can only store values which are in the range from 0 to 2³²-1.

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

new Array(Math.pow(2, 40))
new Array(-1)
new ArrayBuffer(Math.pow(2, 32))
new ArrayBuffer(-1)

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

let b = new Array(Math.pow(2, 32) - 1);
b.length = b.length + 1;         // set 2^32 to the length property

Valid cases

[ Math.pow(2, 40) ]                     // [ 1099511627776 ]
[ -1 ]                                  // [ -1 ]
new ArrayBuffer(Math.pow(2, 32) - 1)
new ArrayBuffer(0)

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

let 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)