Develop Reference

Javascript loop calculation

Using the below script
var lvl = 0;
var HappB = 5;
var DecoX = 5;
var DecoY = 5;
while (lvl < 5) {
document.ofrm.UpgSD.value += Math.ceil((Math.exp((HappB + lvl) / ((DecoX * DecoY) * 1.8))) * 1 * 130000 * (Math.tanh((lvl + 1) / 20)) * (Math.tanh((lvl + 1) / 20)));
lvl++;
}
<form name="ofrm">
<input type="text" name="UpgSD" size="50" tabindex="1">
</form>
The result is
363147633676050952513778
The expected output is
363 + 1476 + 3367 + 6050 + 9525 + 13778 = 34559
How can I fix this?

Here's an updated code.
1. Your loop condition needs to be corrected.
2. .value is string. You can set to a variable and then attach it.
var lvl = 0;
var HappB = 5;
var DecoX = 5;
var DecoY = 5;
var number = 0;
while (lvl <= 5) {
number += Math.ceil((Math.exp((HappB + lvl) / ((DecoX * DecoY) * 1.8))) * 1 * 130000 * (Math.tanh((lvl + 1) / 20)) * (Math.tanh((lvl + 1) / 20)));
lvl++;
}
document.ofrm.UpgSD.value = number;
<form name="ofrm">
<input type="text" name="UpgSD" size="50" tabindex="1">
</form>

It looks like document.ofrm.UpgSD.value is being cast into a string (rather than a number).
var lvl = 0;
var HappB = 5;
var DecoX = 5;
var DecoY = 5;
var initialValue = parseInt(document.ofrm.UpgSD.value);
while (lvl < 5) {
initialValue += Math.ceil((Math.exp((HappB + lvl) / ((DecoX * DecoY) * 1.8))) * 1 * 130000 * (Math.tanh((lvl + 1) / 20)) * (Math.tanh((lvl + 1) / 20)));
lvl++;
}
document.ofrm.UpgSD.value = initialValue;

How to write multidimensional array in JS in a loop?

I have the following code:
var marketReturns = [1];
var marketReturnsVol = [1];
var marketVolatility = [1];
var yearlyReturns = [];
var yearlyReturns2 = [];
for (y = 0; y < 50000; y++) {
for (x = 1; x <= 251; x++) {
do {
var rand1 = Math.random();
var rand2 = Math.random();
var x1 = 2.0 * rand1 - 1.0;
var x2 = 2.0 * rand2 - 1.0;
var w = Math.pow(x1, 2) + Math.pow(x2, 2);
} while (w === 0 || w > 1);
multiplier = Math.sqrt((-2 * Math.log(w)) / w);
var volVol = 1 + (((x2 * multiplier) / 100) * 5.98); // real ^VIX is 5.98.
marketVolatility[x] = volVol * marketVolatility[x - 1];
var y1 = 1 + (((x1 * multiplier) / 100) * 1.07); // 1.07 is the daily vol of ^GSPC
var y12 = 1 + (((x1 * multiplier) / 100) * 1.07 * marketVolatility[x]) + 0.00038; // 1.07 is the daily vol of ^GSPC
marketReturns[x] = y1 * marketReturns[x - 1];
marketReturnsVol[x] = y12 * marketReturnsVol[x - 1];
}
yearlyReturns[y] = marketReturns[251];
yearlyReturns2[y] = marketReturnsVol[251];
}
yearlyReturns.sort(function (a, b) {
return (a - b);
})
yearlyReturns2.sort(function (a, b) {
return (a - b);
})
for (x = 0; x < yearlyReturns.length; x++) {
document.write(yearlyReturns2[x] + ", ");
}
So essentially I am calculating marketReturns, which is marketReturns[x-1] * daily change. I want however to make this into subarrays where I can preserve all the individual marketReturns for each iteration of y instead of just preserving the last day like I am in yearlyReturns[y].
I thought I could do it as such:
marketReturns[y][x] = y1 * marketReturns[y][x - 1];
marketReturnsVol[y][x] = y12 * marketReturnsVol[y][x - 1];
But this doesn't work. Is there any way for me to start writing the marketReturns figures into subarrays? Thanks.

You can mimic the multidimensional array using nested array/nested object in javascript:
e.g.
var arr = [];
//Initialize a 10x10 "multidimensional" array
for(var i = 0; i < 10; i++) {
arr[i] = [];
for(var j = 0; j < 10; j++) {
arr[i][j] = 0;
}
}
//Store
arr[5][5] = 10;

Refactor a for() loop using Math.pow()?

Here's a question that I'm hoping will improve my programming chops. I have this loop that is calculating a future sum based on annual payments, increased by interest and devalued by inflation (it's derived from the PV function in Excel):
var pmt = 66,449.75 // annual payment
var ip = 0.03 // interest rate
var fv = 0 // future value, not require here
var k = 1 // interest is applied at beginning / end of period
var n = 25 // number of periods (years in this case)
var ri = 0.025 // rate of inflation
var pv = 0;
for (var i = n - 1; i >= 0; i -= 1) {
pv = (pv + (pmt * k - fv) * Math.pow(1 + ri, i)) / (1 + ip);
}
Is it possible to use Math.pow() to reproduce what this loop is doing?

To simplify, I rename some expressions
a = pmt * k - fv;
b = 1 + ri;
c = 1 + ip;
x = pv;
So your code becomes
for (var i = n - 1; i >= 0; --i) {
x = x / c + a * Math.pow(b, i) / c;
}
Then
x_0
x_1 = x_0 / c + a b^{n-1} / c
x_2 = x_1 / c + a b^{n-2} / c = x_0 / c^2 + a b^{n-1} / c^2 + a b^{n-2} / c
...
x_i = x_{i-1} / c + a b^{n-i} / c = x_0 / c^i + \sum_{k=1}^i a b^{n-k} / c^{i-k+1}
...
x_n = x_0 / c^n + \sum_{k=1}^n a * b^{n-k} / c^{n-k+1}
According to WolframAlpha,
x_n = x_0 / c^n + a (b^n-c^n) / (c^n (b-c))
Therefore, instead of your loop you can use
var foo = Math.pow(1 + ip, n); // c^n
pv = pv / foo + (pmt*k-fv) * (Math.pow(1+ri,n) - foo) / foo / (ri-ip);

financial rate function in javascript not working properly

the function given at
simple financial rate function in javascript
is not giving me same answers as excel rate function some time. It works perfectly for the problem given at http://allfinancialmatters.com/2009/11/03/how-to-use-the-rate-function-in-excel/ but for my test cases. its results are different from excel rate. this is strange behaviour. i am unable to sort this out. my test cases (with excel output) are
RATE(360,-665.3, 99000) = 0.0059
RATE(360,-958.63, 192000) =0.0036
RATE(180,-1302.96,192000) = 0.0023
RATE(360, -889.19, 192000) =0.00312
RATE(360, -1145.8, 240000) = 0.0033
my code.js is
function rate(paymentsPerYear, paymentAmount, presentValue, futureValue, dueEndOrBeginning, interest)
{
//If interest, futureValue, dueEndorBeginning was not set, set now
//if (interest == null) // not working here :D
if (isNaN(interest))
interest = 0.1;
//interest = 0.1;
if (isNaN(futureValue))
futureValue = 0;
if (isNaN(dueEndOrBeginning))
dueEndOrBeginning = 0;
var FINANCIAL_MAX_ITERATIONS = 128;//Bet accuracy with 128
var FINANCIAL_PRECISION = 0.0000001;//1.0e-8
var y, y0, y1, x0, x1 = 0, f = 0, i = 0;
var rate = interest; // initiallizing rate to our guess interest
if (Math.abs(rate) < FINANCIAL_PRECISION)
{
y = presentValue * (1 + paymentsPerYear * rate) + paymentAmount * (1 + rate * dueEndOrBeginning) * paymentsPerYear + futureValue;
}
else
{
f = Math.exp(paymentsPerYear * Math.log(1 + rate));
y = presentValue * f + paymentAmount * (1 / rate + dueEndOrBeginning) * (f - 1) + futureValue;
}
y0 = presentValue + paymentAmount * paymentsPerYear + futureValue;
y1 = presentValue * f + paymentAmount * (1 / rate + dueEndOrBeginning) * (f - 1) + futureValue;
// find root by Newton secant method
i = x0 = 0.0;
x1 = rate;
while ((Math.abs(y0 - y1) > FINANCIAL_PRECISION)
&& (i < FINANCIAL_MAX_ITERATIONS))
{
rate = (y1 * x0 - y0 * x1) / (y1 - y0);
x0 = x1;
x1 = rate;
if (Math.abs(rate) < FINANCIAL_PRECISION)
{
y = presentValue * (1 + paymentsPerYear * rate) + paymentAmount * (1 + rate * dueEndOrBeginning) * paymentsPerYear + futureValue;
}
else
{
f = Math.exp(paymentsPerYear * Math.log(1 + rate));
y = presentValue * f + paymentAmount * (1 / rate + dueEndOrBeginning) * (f - 1) + futureValue;
}
y0 = y1;
y1 = y;
++i;
}
return rate;
//return String(parseFloat(rate).toFixed(3)); // rounding it to 3 decimal places
//return parseFloat(rate).toFixed(3);
}
and my HTML file is
<head><title>JavaScript Loan Calculator</title>
<script src="code.js"></script>
</head>
<body bgcolor="white">
<form name="loandata">
<table>
<tr>
<td>1)</td>
<td>paymentsPerYear:</td>
<td><input type="text" name="paymentsPerYear" size="12"
onchange="calculate();"></td>
</tr>
<tr>
<td>2)</td>
<td>paymentAmount:</td>
<td><input type="text" name="paymentAmount" size="12"
onchange="calculate();"></td>
</tr>
<tr>
<td>3)</td>
<td>presentValue:</td>
<td><input type="text" name="presentValue" size="12"
onchange="calculate();"></td>
</tr>
<tr>
<td>4)</td>
<td>futureValue:</td>
<td><input type="text" name="futureValue" size="12"></td>
</tr>
<tr>
<td>5)</td>
<td>dueEndOrBeginning:</td>
<td><input type="text" name="dueEndOrBeginning" size="12"></td>
</tr>
<tr>
<td>6)</td>
<td>interest:</td>
<td><input type="text" name="interest" size="12"></td>
</tr>
<tr><td colspan="3">
<input type="button" value="Compute" onClick="calculate();">
</td></tr>
<tr>
<td>APR:</td>
<td><input type="text" name="APR" id="APR" size="12"></td>
</tr>
</table>
</form>
<script language="JavaScript">
function calculate() {
var paymentsPerYear = document.loandata.paymentsPerYear.value;
var paymentAmount = document.loandata.paymentAmount.value;
var presentValue = document.loandata.presentValue.value;
var futureValue = document.loandata.futureValue.value;
var dueEndOrBeginning = document.loandata.dueEndOrBeginning.value ;
var interest = document.loandata.interest.value ;
var ans = rate(parseFloat(paymentsPerYear), parseFloat(paymentAmount), parseFloat(presentValue), parseFloat(futureValue), parseFloat(dueEndOrBeginning), parseFloat(interest));
document.loandata.APR.value=ans;
//alert(futureValue);
}
</script>
</body>
</html>

In case anyone is still looking for a javascript implementation of the Excel's Rate function, this is what I came up with:
var rate = function(nper, pmt, pv, fv, type, guess) {
// Sets default values for missing parameters
fv = typeof fv !== 'undefined' ? fv : 0;
type = typeof type !== 'undefined' ? type : 0;
guess = typeof guess !== 'undefined' ? guess : 0.1;
// Sets the limits for possible guesses to any
// number between 0% and 100%
var lowLimit = 0;
var highLimit = 1;
// Defines a tolerance of up to +/- 0.00005% of pmt, to accept
// the solution as valid.
var tolerance = Math.abs(0.00000005 * pmt);
// Tries at most 40 times to find a solution within the tolerance.
for (var i = 0; i < 40; i++) {
// Resets the balance to the original pv.
var balance = pv;
// Calculates the balance at the end of the loan, based
// on loan conditions.
for (var j = 0; j < nper; j++ ) {
if (type == 0) {
// Interests applied before payment
balance = balance * (1 + guess) + pmt;
} else {
// Payments applied before insterests
balance = (balance + pmt) * (1 + guess);
}
}
// Returns the guess if balance is within tolerance. If not, adjusts
// the limits and starts with a new guess.
if (Math.abs(balance + fv) < tolerance) {
return guess;
} else if (balance + fv > 0) {
// Sets a new highLimit knowing that
// the current guess was too big.
highLimit = guess;
} else {
// Sets a new lowLimit knowing that
// the current guess was too small.
lowLimit = guess;
}
// Calculates the new guess.
guess = (highLimit + lowLimit) / 2;
}
// Returns null if no acceptable result was found after 40 tries.
return null;
};
Testing the function with Abdul's test cases give the following results:
rate(360,-665.3, 99000);
0.005916521358085446
rate(360,-958.63, 192000);
0.0036458502960158515
rate(180,-1302.96,192000);
0.0022917255526408564
rate(360, -889.19, 192000);
0.0031250616819306744
rate(360, -1145.8, 240000);
0.003333353153720964

Automatically fire a JavaScript code after loading a page in Google Chrome

I have a Javascript code, which I use to bring Night Mode effect on an HTML page...
The code goes something like this-
javascript: (function () {
function RGBtoHSL(RGBColor) {
with(Math) {
var R, G, B;
var cMax, cMin;
var sum, diff;
var Rdelta, Gdelta, Bdelta;
var H, L, S;
R = RGBColor[0];
G = RGBColor[1];
B = RGBColor[2];
cMax = max(max(R, G), B);
cMin = min(min(R, G), B);
sum = cMax + cMin;
diff = cMax - cMin;
L = sum / 2;
if (cMax == cMin) {
S = 0;
H = 0;
} else {
if (L <= (1 / 2)) S = diff / sum;
else S = diff / (2 - sum);
Rdelta = R / 6 / diff;
Gdelta = G / 6 / diff;
Bdelta = B / 6 / diff;
if (R == cMax) H = Gdelta - Bdelta;
else if (G == cMax) H = (1 / 3) + Bdelta - Rdelta;
else H = (2 / 3) + Rdelta - Gdelta; if (H < 0) H += 1;
if (H > 1) H -= 1;
}
return [H, S, L];
}
}
function getRGBColor(node, prop) {
var rgb = getComputedStyle(node, null).getPropertyValue(prop);
var r, g, b;
if (/rgb\((\d+),\s(\d+),\s(\d+)\)/.exec(rgb)) {
r = parseInt(RegExp.$1, 10);
g = parseInt(RegExp.$2, 10);
b = parseInt(RegExp.$3, 10);
return [r / 255, g / 255, b / 255];
}
return rgb;
}
function hslToCSS(hsl) {
return "hsl(" + Math.round(hsl[0] * 360) + ", " + Math.round(hsl[1] * 100) + "%, " + Math.round(hsl[2] * 100) + "%)";
}
var props = ["color", "background-color", "border-left-color", "border-right-color", "border-top-color", "border-bottom-color"];
var props2 = ["color", "backgroundColor", "borderLeftColor", "borderRightColor", "borderTopColor", "borderBottomColor"];
if (typeof getRGBColor(document.documentElement, "background-color") == "string") document.documentElement.style.backgroundColor = "white";
revl(document.documentElement);
function revl(n) {
var i, x, color, hsl;
if (n.nodeType == Node.ELEMENT_NODE) {
for (i = 0; x = n.childNodes[i]; ++i) revl(x);
for (i = 0; x = props[i]; ++i) {
color = getRGBColor(n, x);
if (typeof (color) != "string") {
hsl = RGBtoHSL(color);
hsl[2] = 1 - hsl[2];
n.style[props2[i]] = hslToCSS(hsl);
}
}
}
}
})()
I have saved this as a Bookmarklet in my Bookmark Bar on Google Chrome, but I want this to be automatically applied to every page I load. What should I do to achieve this?

You should write this as a userscript and run it with something like tampermonkey