CODEWITHSUNDEEP
javascriptmath
Caleb Whittington
Caleb Whittington

Reputation: 101

How to check for exponential values in Javascript

I am streaming data from a CSV file and I am pushing certain values to an array. Some of these values are very large, and may be exported as exponential values (e.g. 5.02041E+12) and some may be normal values. I'd like to have an if statement that checks to see if these values are exponential or not, and if they are I will pass them to a function that converts them into 'normal' numbers (e.g. 5020410000000). Is there a quick way to do this?

(These values are passed to an API call which is why they need to be converted to 'normal' values)

Example of what this may look like:

valueOne = 5.02041E+12;
valueTwo = 1234;

if (valueOne.isExponential) {
  **pass to converting function**
}

//Output = 5020410000000

if (valueTwo.isExponential) {
  **pass to converting function**
}

//Output = 1234 (unchanged)

I'd expect all values in the array to therefore be 'normal' values (i.e. NOT is exponential form)

Upvotes: 4

Views: 8798

Answers (3)

tevemadar
tevemadar

Reputation: 13225

Numbers are numbers, the values 5.02041E+12 and 5020410000000 do not differ internally:

// values in code:
var withe=5.02041E+12;
var withoute=5020410000000;
console.log(withe,"?=",withoute,withe===withoute);

// values parsed from strings:
var stringwithe="5.02041E+12";
var stringwithoute="5020410000000";
var a=parseFloat(stringwithe);
var b=parseFloat(stringwithoute);
console.log(a,"?=",b,a===b);

And you can also see that when you simply display a number, it will not use the scientific notation by default, actually you would have to ask for it via using toExponential()

One thing you can worry about is the internal precision of Number. It has a method isSafeInteger() and various fields, like MAX_SAFE_INTEGER. Surpassing that value can lead to unexpected results:

var a=Number.MAX_SAFE_INTEGER;
console.log("This is safe:",a,Number.isSafeInteger(a));
a++;
for(var i=0;i<5;i++)
  console.log("These are not:",a++,Number.isSafeInteger(a));

So the loop can not increment a any further, because there is no such number as 9007199254740993 here. The next number which exists after 9007199254740992 is 9007199254740994. But these numbers are more than 1000x greater than the 5020410000000 in the question.

Upvotes: 1

silicakes
silicakes

Reputation: 6902

You can just use toPrecision on every number and ensure it converts

const valueOne = 5.02041E+12;
const valueTwo = 1234;

const precisionValueOne = valueOne.toPrecision(); // "5020410000000"
const precisionValue2 = valueTwo.toPrecision(); // "1234"

You can then, optionally convert it back to numbers:

sanitizedValueOne = Number(precisionValueOne); // 5020410000000
sanitizedValueTwo = Number(precisionValueTwo); // 1234

Upvotes: 0

MikeB
MikeB

Reputation: 623

Do a RegExp match for E+ and probably for E-

The 'number' you are starting with must be text, but you should do a bit of sanity checking too. Might be a good idea to check whether it is larger than MaxInt before you try any Math-based conversions.

Upvotes: 0

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