TypeError: can't convert x to BigInt
The JavaScript exception "x can't be converted to BigInt" occurs when attempting to convert a Symbol
, null
, or undefined
value to a BigInt
, or if an operation expecting a BigInt parameter receives a number.
Message
TypeError: Cannot convert null to a BigInt (V8-based) TypeError: can't convert null to BigInt (Firefox) TypeError: Invalid argument type in ToBigInt operation (Safari)
Error type
What went wrong?
When using the BigInt()
function to convert a value to a BigInt, the value would first be converted to a primitive. Then, if it's not one of BigInt, string, number, and boolean, the error is thrown.
Some operations, like BigInt.asIntN
, require the parameter to be a BigInt. Passing in a number in this case will also throw this error.
Examples
Using BigInt() on invalid values
js
const a = BigInt(null);
// TypeError: can't convert null to BigInt
const b = BigInt(undefined);
// TypeError: can't convert undefined to BigInt
const c = BigInt(Symbol("1"));
// TypeError: can't convert Symbol("1") to BigInt
js
const a = BigInt(1);
const b = BigInt(true);
const c = BigInt("1");
const d = BigInt(Symbol("1").description);
Note: Simply coercing the value to a string or number using String()
or Number()
before passing it to BigInt()
is usually not sufficient to avoid all errors. If the string is not a valid integer number string, a SyntaxError is thrown; if the number is not an integer (most notably, NaN
), a RangeError is thrown. If the range of input is unknown, properly validate it before using BigInt()
.
Passing a number to a function expecting a BigInt
js
const a = BigInt.asIntN(4, 8);
// TypeError: can't convert 8 to BigInt
const b = new BigInt64Array(3).fill(3);
// TypeError: can't convert 3 to BigInt
js
const a = BigInt.asIntN(4, 8n);
const b = new BigInt64Array(3).fill(3n);