javascriptnumbers

How to compare two big number in javascript

Why below code output result is equal? How to compare?

var num1 = 340282000000000000000000000000000000001
var num2 = 340282000000000000000000000000000000000  // 3.402823E+38
if(num1 == num2) {
    console.log('num1 equal to num2');
} else if(num1 > num2) {
    console.log('num1 bigger than num2');
} else {
    console.log('num1 lower than num2')
}
Solution

  • Note that exponential notation is not meant for precision, it's an imprecise number, most of the time.

    Both numbers provided result in the same exponential number.

    It's possible to convert a big number to big integer just adding the suffix n:

    // NOTE THAT ALL NUMBERS ARE INTEGER

let num1 = 340282000000000000000000000000000000001;
let num2 = 340282000000000000000000000000000000000;
let num3 = 340282000000000000000000000000000000001n;
let num4 = 340282000000000000000000000000000000000n;
let numC = BigInt(3.40282e+38);

console.log('num1 =', String(num1));
console.log('num2 =', String(num2));
console.log('num3 =', String(num3));
console.log('num4 =', String(num4));
console.log('numC = 3.40282e+38 =', String(numC));

console.log('num1 == num2?', num1 == num2);
console.log('num3 == num4?', num3 == num4);