JavaScript Summing Large Integers

JavaScript summing large integers

JavaScript uses floating point internally.

What is JavaScript's highest integer value that a number can go to without losing precision?

In other words you can't use more than 53 bits. In some implementations you may be limited to 31.

Try storing the bits in more than one variable, use a string, or get a bignum library, or if you only need to deal with integers, a biginteger library.

How to add two big numbers in javascript?

Input the numbers as string and add each characters each other as array something like this:

 function add() {
        document.getElementById("demo").innerHTML = "";
        var x = document.getElementById("txt1").value;
        var y = document.getElementById("txt2").value;
        var len;
        var lenx = x.length;
        var leny = y.length;
        var x1,y1,rem,div=0;
        if(lenx>leny) len = lenx; else len = leny;

        for(var i=0;i<len;i++){
            if(i>=lenx) x1  = 0;
            else x1 = parseInt(x[lenx-i-1]);
            if(i>=leny) y1 = 0;
            else y1 = parseInt(y[leny-i-1]);
            rem = (x1+y1+div)%10;
            div = Math.floor((x1 + y1+div)/10);
            document.getElementById("demo").innerHTML = rem + document.getElementById("demo").innerHTML;
        }
       if(div>0){
            document.getElementById("demo").innerHTML = div + document.getElementById("demo").innerHTML;
       }
    }

Here the code: https://jsfiddle.net/mtsL1k2x/5/

Note: this is only for natural numbers. You can modify depending on your inputs

Adding two big numbers in javascript

For doing operations with such big integers, you should use BigInt, it will correctly operate on integers bigger than 2ˆ53 (which is the largest size that normal Number can support on JS

const sum = BigInt(76561197960265728) + BigInt(912447736);

console.log(sum.toString());

Sum Big Integers

The problem is that in that specific kata (IIRC), the numbers stored in a and b are too large for a regular 32 bit integer, and floating point arithmetic isn't exact. Therefore, your version does not return the correct value:

sumStrings('100000000000000000000', '1')
// returns '100000000000000000000' instead of '100000000000000000001'

You have to make sure that this does not happen. One way is to do an good old-fashioned carry-based addition and stay in the digit/character based world throughout the whole computation:

function sumStrings(a, b) {
   var digits_a = a.split('')
   var digits_b = b.split('')
   ...
}

Extremely large numbers in javascript

You are going to need a javascript based BigInteger library. There are many to choose from. Here is one https://github.com/peterolson/BigInteger.js

You can use it like this

var n = bigInt("91942213363574161572522430563301811072406154908250")
    .plus("91942213363574161572522430563301811072406154908250");

JavaScript not adding large numbers correctly (but getting very close)

JavaScript uses IEEE-754 64-bit doubles as its number format. These cannot represent arbitrarily precise values; they become incorrect when you exceed a certain threshold and begin instead storing values that are close to (but not quite exactly) the actual values. According to this earlier answer, the largest value that can be stored accurately is 2⁵³, which is about 9 × 10¹⁵. Your number (which is about 1.3 × 10¹⁷) is larger than this, so (with good probability) it cannot be represented accurately.

If you want to get the exact answer in JavaScript, you will need to use a library that supports arbitrary-precision integers. A quick Google search turned up this library, but I can't vouch for how accurate it is.

Hope this helps!

Sum all the digits of a number Javascript

Basically you have two methods to get the sum of all parts of an integer number.

With numerical operations
Take the number and build the remainder of ten and add that. Then take the integer part of the division of the number by 10. Proceed.

var value = 2568,
    sum = 0;

while (value) {
    sum += value % 10;
    value = Math.floor(value / 10);
}

console.log(sum);

JavaScript Summing Large Integers