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I am trying to convert an array of numbers into one single number, for example 

[1,2,3] to 123.

However, my code can't handle big arrays since it can’t return exact number. Such as 

[6,1,4,5,3,9,0,1,9,5,1,8,6,7,0,5,5,4,3] returns 6145390195186705000

Is there any way that I could properly convert into a single number.I would really appreciate any help. 

var integer = 0;
var digits = [1,2,3,4]
//combine array of digits into int
digits.forEach((num,index,self) => {
    integer += num * Math.pow(10,self.length-index-1)
});
lmngn23
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    Use BigInt libraries or save them as string and manipulate them as number – quirimmo Jan 03 '19 at 09:09
  • Check out [enter link description here](https://stackoverflow.com/questions/307179/what-is-javascripts-highest-integer-value-that-a-number-can-go-to-without-losin). You number is higher than max safe integer in js – deathangel908 Jan 03 '19 at 09:09
  • Possible duplicate of [What is JavaScript's highest integer value that a number can go to without losing precision?](https://stackoverflow.com/questions/307179/what-is-javascripts-highest-integer-value-that-a-number-can-go-to-without-losin) – Peter B Jan 03 '19 at 09:12

3 Answers3

3

The biggest integer value javacript can hold is +/- 9007199254740991. Note that the bitwise operators and shift operators operate on 32-bit ints, so in that case, the max safe integer is 2^31-1, or 2147483647.

In my opinion, you can choose one of the following:

  • store the numbers as strings and manipulate them as numbers; you might have to implement special functions to add/subtract/multiply/divide them (these are classic algorithmic problems)

  • use the BigInt; BigInts are a new numeric primitive in JavaScript that can represent integers with arbitrary precision. With BigInts, you can safely store and operate on large integers even beyond the safe integer limit. Unfortunately, they work only with Chrome right now. If you want to work with other browsers, you might check this or even this if you work with angularjs or nodejs.

Try the following code in the Chrome's console:

let x = BigInt([6,1,4,5,3,9,0,1,9,5,1,8,6,7,0,5,5,4,3].join(''));
console.log(x);

This will print 6145390195186705543n. The n suffix marks that it is a big integer.

Cheers!

Adrian Pop
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  • Thank you. Actually I am doing a programming exercise called "Add one" and the tests environment does not allow me to use BigInt. – lmngn23 Jan 03 '19 at 09:41
  • @user545871 You are welcome! You may mark my answer as accepted if it was helpful :) Cheers! – Adrian Pop Jan 03 '19 at 10:18
2

You can use JavaScript Array join() Method and parse it into integer. Example: parseInt([6,1,4,5,3,9,0,1,9,5,1,8,6,7,0,5].join('')) results: 6145390195186705

Edited: Use BigInt instead of parseInt , but it works only on chrome browser.

sumit gautam
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The largest number possible in Javascript is +/- 9007199254740991

Use BigInt. Join all numbers as a string and pass it in BigInt global function to convert it into int

var integer = 0;
var digits = [1,2,3,4]
//combine array of digits into int
digits.forEach((num,index,self) => {
    integer += num;
});
integer= BigInt(integer);

Note : Works only on Chrome as of now. You can use othee libraries like BigInteger.js or MathJS

Sandesh Gupta
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