TypeError: can't convert x to BigInt
The JavaScript exception "x can't be converted to BigInt" occurs when attempting to convert aSymbol,null, orundefined value to aBigInt, 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 theBigInt() 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, likeBigInt.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
const a = BigInt(null);// TypeError: can't convert null to BigIntconst b = BigInt(undefined);// TypeError: can't convert undefined to BigIntconst c = BigInt(Symbol("1"));// TypeError: can't convert Symbol("1") to BigIntconst 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 usingString() orNumber() before passing it toBigInt() is usually not sufficient to avoid all errors. If the string is not a valid integer number string, aSyntaxError is thrown; if the number is not an integer (most notably,NaN), aRangeError is thrown. If the range of input is unknown, properly validate it before usingBigInt().
Passing a number to a function expecting a BigInt
const a = BigInt.asIntN(4, 8);// TypeError: can't convert 8 to BigIntconst b = new BigInt64Array(3).fill(3);// TypeError: can't convert 3 to BigIntconst a = BigInt.asIntN(4, 8n);const b = new BigInt64Array(3).fill(3n);