I have the variable y, which is a subtotal. Its value is different depending on what happens with the html, but throughout the script I declared it like this:
var y = 21.78;
etc. Why is it that on my last equation where I add up the total, it treats them as strings when I want to add the values?
var tax = (0.055*y).toFixed(2);
var totalprice = y+tax;
/* totalprice holds "21.781.20" instead of 22.98 */
According to:
https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Number/toFixed
toFixed() returns:
A string representation of number that does not use exponential
notation and has exactly digits digits after the decimal place.
thus, y+tax is cast to a string since one of the operands is a string.
In my opinion, this would make sense as Javascript's intrinsic numeric types do not have the ability to store a specific number of decimal place digits, so a string would be the most appropriate data structure to store this with.
I would advise you do all your addition before calling toFixed(), since the method is most suitable for formatting display output.
var taxRate = 0.055;
var subtotal = 21.78;
var tax = (taxRate * subtotal).toFixed(2),
totalprice = ((1+taxRate) * subtotal).toFixed(2);
document.write(totalprice);
The .toFixed() method returns a string. Try applying that method as the last step after all other calculations.
Here's a simple fix. Put '+' in front of the tax variable to convert it to a number.
var y = 21.78;
var tax = (0.055*y).toFixed(2);
var totalprice = y+ (+tax);
totalprice === 22.98;
If you don't want any rounding errors when you use toFixed, then include this re-implementation of it in your script.
http://bateru.com/news/2012/03/reimplementation-of-number-prototype-tofixed/
In my experience, if there's any chance available, Javascript will see the "+" sign as concatenate rather than addition. It's driven me nuts on more than one occasion. I will generally do this rather than chance concatenation:
var totalprice = parseInt(y)+parseInt(tax);
When letter replaces value, multiply with 1 when you're in need of +.
var totalprice = (y*1) + tax .
Other operands work fine, it's just the + operand that needs special treatment when variable replace value.
Related
I have a JavaScript and HTML form to make a different sums and multiplications. In general, the script works fine, but in some cases, it does not apply the decimal separator and does not display decimal values.
This is the JavaScript when it sums the values well calculated in the precedent script with decimal separator (example: 228.8). This script returns the value of the sum 1040+228.8-208 = 1060) but the really result is 1060.8:
function sumResult() {
var bookSumFT = parseInt(document.getElementById("bookSum").value);
var bookRivFT = parseInt(document.getElementById("bookRiv").value)
var bookIVTFT = parseInt(document.getElementById("bookIVT").value)
var bookRitFT = parseInt(document.getElementById("bookRit").value)
document.getElementById("bookAllCalc").value = bookSumFT + bookRivFT + bookIVTFT - bookRitFT;
}
How do I calculate the correct sum with decimal values?
parseInt() will convert your values to integers. That is, without the decimal part.
Use Number() or parseFloat() instead of parseInt()
I am currently creating a site that will help me quickly answer physics questions.
As it happens, the code didn't run as expected, here is the code
if (option == "dv") {
var Vinitial = prompt("What is the Velocity Initial?")
var acceleration = prompt("what is the acceleration?")
var time = prompt("what is the time?")
Vfinal = Vinitial + acceleration * time
displayV.innerHTML = "v= vf= " + Vfinal + "ms" + sup1.sup();
}
Now, let's say Vinitial was 9, acceleration was 2, and time was 3.
When the code runs, instead of getting 15 for "Vfinal", I get 96.
I figured out that it multiplies acceleration and time fine, and then just concatenates the 9 at the beginning, with 6 (the product of 2 * 3).
I have fixed it for now by using
Vfinal = acceleration * time - (-Vinitial)
which avoids using the "+" sign, but I don't want to have to keep doing this. How do I fix it?
you are dealing with strings here, and math operations on strings will mess up. Remember when ever you are doing math operations you have to convert the data into actual numbers and then perform the math.
Use parseInt() more Details here
Your code should change to
Vfinal = parseInt(Vinitial,10) + parseInt(acceleration,10) * parseInt(time,10);
Edit 1: If the numbers are decimal values then use parseFloat() instead
So the code would be
Vfinal = parseFloat(Vinitial) + parseFloat(acceleration) * parseFloat(time);
Object-Oriented JavaScript - Second Edition: As you already know, when you use the plus sign with two numbers, this
is the arithmetic addition operation. However, if you use the plus
sign with strings, this is a string concatenation operation, and it
returns the two strings glued together:
var s1 = "web";
var s2 = "site";
s1 + s2; // website
The dual purpose of the + operator is a source of errors. Therefore,
if you intend to concatenate strings, it's always best to make sure
that all of the operands are strings. The same applies for addition;
if you intend to add numbers, make sure the operands are numbers.
You can use "+" operator with prompt() to convert returned values from string to int
var Vinitial = +prompt("What is the Velocity Initial?");
var acceleration = +prompt("what is the acceleration?");
var time = +prompt("what is the time?");
Explanation:
var a = prompt('Enter a digit');
typeof a; // "string"
typeof +a; // "number"
If you will enter non-digit data +a gives you NaN. typeof NaN is "number" too :)
You will get the same result with parseInt():
var Vinitial = parseInt(prompt("What is the Velocity Initial?"), 10);
var acceleration = parseInt(prompt("what is the acceleration?"), 10);
var time = parseInt(prompt("what is the time?"), 10);
developer.mozilla.org: parseInt(string, radix);
string: The value to parse.
radix: An integer between 2 and 36 that represents the radix (the base in mathematical numeral systems) of the above mentioned string.
Specify 10 for the decimal numeral system commonly used by humans.
Always specify this parameter to eliminate reader confusion and to
guarantee predictable behavior. Different implementations produce
different results when a radix is not specified, usually defaulting
the value to 10.
Epilogue:
Object-Oriented JavaScript - Second Edition: The safest thing to do is to always specify the radix. If you omit the radix, your code
will probably still work in 99 percent of cases (because most often
you parse decimals), but every once in a while it might cause you a
bit of hair loss while debugging some edge cases. For example, imagine
you have a form field that accepts calendar days or months and the
user types 06 or 08.
Epilogue II:
ECMAScript 5 removes the octal literal values and avoids the confusion
with parseInt() and unspecified radix.
The Problem is, Your value has been took it in a form of string .. so convert your value into Int using parseInt(accelaration).. then it will work ..
Vfinal = parseInt(Vinitial) + parseInt(acceleration) * parseInt(time)
//use ParseInt
var a=10,b=10;
var sum=parseInt(a+b);
ex:
parseInt(Vinitial + acceleration) * time
What I'm trying to do is to make a progress bar for donation. My html structure is:
<div class="hgoal" style="text-align: center;">My goal is to raise $<span id="mygoal">9,999.00</span></div>
<div class="donation-total">Total Donation<span id="total-donation">1,000.00</span></div>
my javascript so far is to get the innerHTML value of mygoal and total-donation.
var mygoal = document.getElementById("mygoal").innerHTML;
var totalgoal = document.getElementById("total-donation").innerHTML;
and I'm getting this as a result:
mygoal = "9,999.00";
total-donation = "1,000.00";
I believe this is a string and not an integer, and using parseInt() only give me the first digit number.
Can anyone give me an idea how can I make this into an integer that can use for computation? example:
mygoal + total-donation = 10,999.00
And also, any idea how can i get the percentage of this two varible?
Use .replace(/,/g,'') to replace commas, then you get the magic of type coercion to convert your string to a number during calculation...
var mygoal = document.getElementById("mygoal").innerHTML.replace(/,/g,'');
var totalgoal = document.getElementById("total-donation").innerHTML.replace(/,/g,'');
If you use + on strings, they will be appended to each other, but other mathematical operators (*/- etc...) will first coerce the strings into numbers. To force coercion, you can multiply by 1, or perhaps use Number("123123.123")...
Number(mygoal) + Number(totalgoal); // using addition, so coerce strings to numbers
(mygoal / total_donation) * 100; // does not need coercion
Your main issue is, that your numbers include colons. The parseFloat() call will work, once you replace these colons. You may use the following code to do so:
// define regexp to replace colons
var replaceColons = new RegExp(',', 'g');
// apply regex
num = num.replace(replaceColons, '');
mygoal=parseInt(mygoal.replace(/,/gi,"")) will give you mygoal=9999.
You should use parseFloat(), not parseInt() ...
More, you have to remove the commas from the string, since parseFloat() does not undertsand number formatting characters (like comma). So, for example:
mygoal = mygoal.replace(/,/g, '');
total_donation = total_donation.replace(/,/g, '');
To get the percentage of two numbers, use:
(mygoal / total_donation) * 100;
Note that in JavaScript you can't use 'minus' char (-) in variables names.
You could use for example 'underscore' char (_), or CamelCase, wich is the recommended style for variables in JavaScript.
You need to convert those Indian (maybe) numbers to valid Javascript numbers for the sum, then convert the output back to the initial format using Number.toLocaleString.
var mygoal = "9,999.00";
var total_donation = "1,000.00";
var total = Number((Number(mygoal.replace(/,/g, '')) + Number(total_donation.replace(/,/g, ''))).toFixed(2));
var finalResult = total.toLocaleString('en-IN',{minimumFractionDigits: 2 });
alert(finalResult);
I'm coding a price calculator in JS and I'm stuck with one formula:
number = (parseFloat(newnumber, 10) * parseFloat(1.536, 10)).toString(10);
I want to add 7.44 to the value of newnumber, before it is multiplied with 1.536
I've tried several things, but with no success.
Going to submit this as an answer, even though someone has put this up a comment while I was typing my answer.
number = ((+newnumber + 7.44) * 1.536).toString();
That should give you a string representation of the summed value.
Use parentheses to make the addition before the multiplication.
number = ((parseFloat(newnumber) + 7.44) * 1.536).toString();
Notes: parseFloat doesn't have a radix parameter. There is no reason to parse the number 1.536, that will only turn it to a string and then back to the same number again. The default for the radix parameter for toString is 10, so that isn't needed.
number = ((parseFloat(newnumber) + 7.44) * parseFloat(1.536)).toString();?
Just use parentheses to separate out the operations. Simple fix.
Working DEMO
Try the following code -
var newnumber = '1';
var number = ((parseFloat(newnumber) + 7.44) * parseFloat(1.536)).toString(10);
alert(number);
I was trying with following script
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script type="text/javascript">
$(document).ready(function() {
$('#item1_number_1').keyup(function() {
var valone = $('#item1_number_1').val();
var valtwo = 5;
var total = ((valone) + (valtwo));
$('#item2_number_1').val(total.toFixed(2));
});
});
</script>
I do not get any result in the field. But when I assign multiple (*) instead of plus (+), I am getting result.
I cannot understand what the error is in "var total = ((valone) + (valtwo));"
You can only call toFixed on Numbers.
String * String will convert the strings to Numbers and multiply them giving you a Number.
String + String will concatenate the two Strings together giving you a String.
You need to convert the strings to Numbers manually before you try to add them together.
var total = (+valone) + (+valtwo);
Then Number + Number will add the two Numbers together giving you a Number.
The value of an input is always a string. "Adding" a string concatenates, giving another string. Strings do not have a toFixed method.
* however is unambiguously "multiply", giving a number and therefore a result.
var valone = parseFloat(document.getElementById('item1_number_1').value);
Use parseInt() to convert fetched value(valone ) to number, and calculate, something like this, please use this only when your number is not float(56.66),
var valone = parseInt($('#item1_number_1').val(), 10);
var valtwo = 5;
var total = ((valone) + (valtwo));
The fetched vaue is treated like string until you convert it into number.
UPDATE
After Archer pointed out, I came to know you are using toFixed() method, which supposed to expect float numbers. So in this case you should use parseFloat() as given below.
var valone = parseFloat($('#item1_number_1').val());
I think one of them is a string. Try parseInt(valone) to make it an int first.
The issue is the + operator can also be used to concat strings together. The * operator is ONLY for multiplication and therefore it implicitly converts your values to numbers.
So you either need to use parseInt, parseFloat, or Number to explicitly convert to a numeric type before using the + operator.