I want to check if a number is a BigInt in an acceptable size if statement
I know there is this try/catch solution:
function isBigInt(x) {
try {
return BigInt(x) === x;
} catch(error) {
return false;
}
}
I want to implement the test directly in an if statement and not as a function.
Can someone help me with this?
You can use typeof. If the number is a BigInt, the typeof would be "bigint". Otherwise, it will be "number"
var numbers = [7, BigInt(7), "seven"];
numbers.forEach(num => {
if (typeof num === "bigint") {
console.log("It's a BigInt!");
} else if (typeof num === "number") {
console.log("It's a number!");
} else {
console.log("It's not a number or a BigInt!");
}
});
typeof num === 'object'
An easy solution would simply be (assuming you only work with numbers):
Number.prototype.bigInt = false
BigInt.prototype.bigInt = true
And then you could simply call myNum.bigInt to check.
NOTE: 3.bigInt will not work because 3. is considered a number, so you could do:
(3).bigInt
3 .bigInt
or use it on a variable
Quick suggestion:
if (BigInt(n) === n.valueOf()) {
// is BigInt
} else {
// not a BigInt
}
Handles both literal BigInt such as 123n, and an Object-wrapped one: Object(123n). Both forms are valid BigInts with different typeof results: "bigint" vs an "object".
If you're only interested to see if the value is a native BigInt, I think @Rojo's suggestion to use
typeof value === 'bigint'
is the best.
But if the BigInt is provided by a custom class (a 'polyfill') then the typeof expression will evaluate to 'object'.
But the following does work:
value.constructor === BigInt
(Note: value instanceof BigInt does not work for the native BigInt type)
A ternary operator can help you, if I understood your question well:
const isBigInt = BigInt(x) === x;
Your variable isBigInt will either be true or false depending on whether your number is a BigInt or not.
And a BigInt object is not strictly equal to Number, but can be in the sense of weak equality.
0n === 0
// ↪ false
0n == 0
// ↪ true
Visit : https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Global_Objects/BigInt for more about BigInt.
cond ? true : false), it's enough to write cond. The problem is with the try..catch, which can't be inlined.