Develop Reference

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)

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.

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

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.

Why I can't convert string to number without losing precision in JS?

We all know that +, Number() and parseInt() can convert string to integer.
But in my case I have very weird result.
I need to convert string '6145390195186705543' to number.
let str = '6145390195186705543';
let number = +str; // 6145390195186705000, but should be: 6145390195186705543
Could someone explain why and how to solve it?

Your number is above the Number.MAX_SAFE_INTEGER (9,007,199,254,740,991), meaning js might have a problem to represent it well.
More information

You are outside the maximum range. Check in your console by typing Number.MAX_SAFE_INTEGER
If you want a number outside this range, take a look into BigInt that allows to define numbers beyond the safe range
https://developers.google.com/web/updates/2018/05/bigint
Read the documentation well before using it since the usage is different than usual

I am guessing this is to solve the plusOne problem in leetcode. As others have answered, you cannot store value higher than the max safe integer. However you can write logic to add values manually.
If you want to add one to the number represented in the array, you can use the below function. If you need to add a different value, you need to tweak the solution a bit.
var plusOne = function(digits) {
let n = digits.length, carry=0;
if(digits[n-1]<9){
digits[n-1] +=1;
} else{
digits[n-1] = 0;
carry=1;
for(let i=n-2;i>=0;i--){
if(digits[i]<9){
digits[i]+=1;
carry=0;
break;
}else{
digits[i]=0;
}
}
if(carry>0){
digits.unshift(carry);
}
}
return digits;
};

Short answer: Your string represents a number to large to fit into the JavaScript number container.
According to the javascript documentation the maximum safe number is 2^53 which is 9007199254740992 source: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number
When you try and convert your number you're creating an overflow exception so you get weird results.

How to get an 8 decimal output?

I am trying to get an 8 decimal output from the following function.
The following function multiplies an input by 2 and then updates this input with the wagerUpdate variable. I would like this outputted number to have 8 decimal places.
For example: if input number is 0.00000001 (this code is for a bitcoin website), then I would like output number to be 0.00000002. For some reason the code below is not working properly as the output number is in the format of 2e-8 without the .toFixed(8) code. Please help if you are able to. Thank you so much.
<script>
function MultiplyWagerFunction() {
var wager = document.getElementById("wagerInputBox").value;
var wagerUpdate = wager*2;
document.getElementById("wagerInputBox").value = +wagerUpdate.toFixed(8);
}
</script>

If you remove the + before wagerUpdate.toFixed(8) it should work fine. wagerUpdate has already be converted to a number when you multiplied it by 2 so there should be no need for the unary +
var a = "0.00000001";
var b = a*2;
console.log(b.toFixed(8));
console.log(+b.toFixed(8));
^ see the difference.
The reason it doesn't work is because what you are doing is equivalent to:
+(b.toFixed(8))
because of the precedence of the operators (member access . is higher than unary +). You are converting b to a string with .toFixed and then converting it back into a number with + and then converting it back into a string again! (this time with the default toString behavior for numbers giving you exponential notation)

Just remove + from +wagerUpdate.toFixed(8); and you would be good.

Instead of:
document.getElementById("wagerInputBox").value = +wagerUpdate.toFixed(8);
try:
document.getElementById("wagerInputBox").innerHTML = +wagerUpdate.toFixed(8);
Why I say so is may be when you set value, browser tries to convert to best possible outcome. But, inner HTML should take the string equivalent!

JavaScript: Retrieve negative floating point number from string of mutiple sums

I have a simple app that allows me to caculate the total amount invoiced and deposited in a route. However I want to allow the user to input multiple values in a single input field; e.g:
500+50+36.5-45.2-10.
I have written a function that will retrieve this input and then split this string into elements of an array at the + sign and immediately parse the values to numbers and then add them and return the total the user inputs into each individual field. This is all well as long as the user does no use any sign other than +.
I have searched the use of regexp:
regular expression in javascript for negative floating point number result stored in array
Javascript Regular expression to allow negative double value?
but none of the results seem to work.
How could I make my code retrieve the values so that the negative values get passed into the array as negative values?
Here is a snippet of my Js code:
For the full code, visit my fiddle.
totalInvoiced: function () {
var a = A.invoiced.value;
var value1Arr = [];
value1Arr = a.split("+").map(parseFloat);
var value1 = 0;
value1Arr.forEach(function (value) {
value1 += value;
});

I really like PhistucK's solution, but here an alternative with regex:
value1Arr = a.split(/(?=\+|\-)/);
This will split it, but keeps the delimiter, so the result will be:
["500", "+50", "+36.5", "-45.2", "-10"]

A bit dirty, but maybe a.replace(/-/g, "+-").split("+"), this way, you add a plus before every minus, since the negative numbers just basically lack an operator.

You can use this pattern that splits on + sign or before - sign:
var str = '500+50+36.5-45.2-10';
console.log(str.split(/\+|(?=-)/));

Javascript convert string to integer

I am just dipping my toe into the confusing world of javascript, more out of necessity than desire and I have come across a problem of adding two integers.
1,700.00 + 500.00
returns 1,700.00500.00
So after some research I see that 1,700.00 is being treated as a string and that I need to convert it.
The most relevant pages I read to resolve this were this question and this page. However when I use
parseInt(string, radix)
it returns 1. Am I using the wrong function or the an incorrect radix (being honest I can't get my head around how I decide which radix to use).
var a="1,700.00";
var b=500.00;
parseInt(a, 10);

Basic Answer
The reason parseInt is not working is because of the comma. You could remove the comma using a regex such as:
var num = '1,700.00';
num = num.replace(/\,/g,'');
This will return a string with a number in it. Now you can parseInt. If you do not choose a radix it will default to 10 which was the correct value to use here.
num = parseInt(num);
Do this for each of your string numbers before adding them and everything should work.
More information
How the replace works:
More information on replace at mdn:
`/` - start
`\,` - escaped comma
`/` - end
`g` - search globally
The global search will look for all matches (it would stop after the first match without this)
'' replace the matched sections with an empty string, essentially deleting them.
Regular Expressions
A great tool to test regular expressions: Rubular and more info about them at mdn
If you are looking for a good tutorial here is one.
ParseInt and Rounding, parseFloat
parseInt always rounds to the nearest integer. If you need decimal places there are a couple of tricks you can use. Here is my favorite:
2 places: `num = parseInt(num * 100) / 100;`
3 places: `num = parseInt(num * 1000) / 1000;`
For more information on parseInt look at mdn.
parseFloat could also be used if you do not want rounding. I assumed you did as the title was convert to an integer. A good example of this was written by #fr0zenFry below. He pointed out that parseFloat also does not take a radix so it is always in base10. For more info see mdn.

Try using replace() to replace a , with nothing and then parseFloat() to get the number as float. From the variables in OP, it appears that there may be fractional numbers too, so, parseInt() may not work well in such cases(digits after decimal will be stripped off).
Use regex inside replace() to get rid of each appearance of ,.
var a = parseFloat('1,700.00'.replace(/,/g, ''));
var b = parseFloat('500.00'.replace(/,/g, ''));
var sum = a+b;
This should give you correct result even if your number is fractional like 1,700.55.
If I go by the title of your question, you need an integer. For this you can use parseInt(string, radix). It works without a radix but it is always a good idea to specify this because you never know how browsers may behave(for example, see comment #Royi Namir). This function will round off the string to nearest integer value.
var a = parseInt('1,700.00'.replace(/,/g, ''), 10); //radix 10 will return base10 value
var b = parseInt('500.00'.replace(/,/g, ''), 10);
var sum = a+b;
Note that a radix is not required in parseFloat(), it will always return a decimal/base10 value. Also, it will it will strip off any extra zeroes at the end after decimal point(ex: 17500.50 becomes 17500.5 and 17500.00 becomes 17500). If you need to get 2 decimal places always, append another function toFixed(decimal places).
var a = parseFloat('1,700.00'.replace(/,/g, ''));
var b = parseFloat('500.00'.replace(/,/g, ''));
var sum = (a+b).toFixed(2); //change argument in toFixed() as you need
// 2200.00
Another alternative to this was given by #EpiphanyMachine which will need you to multiply and then later divide every value by 100. This may become a problem if you want to change decimal places in future, you will have to change multiplication/division factor for every variable. With toFixed(), you just change the argument. But remember that toFixed() changes the number back to string unlike #EpiphanyMachine solution. So you will be your own judge.

try this :
parseFloat(a.replace(/,/g, ''));
it will work also on : 1,800,300.33
Example :
parseFloat('1,700,800.010'.replace(/,/g, '')) //1700800.01

Javascript doesn't understand that comma. Remove it like this:
a.replace(',', '')
Once you've gotten rid of the comma, the string should be parsed with no problem.