I'm doing some simple math in Javascript, but my equation's result is drastically different than what it should be. The math is:
3.05+(((0.32*0)+3.28)+(1+(0.19*0))*(2.66*1^2))*1;
When I did it out by hand, and then used Wolfram Alpha (https://www.wolframalpha.com/) I get the correct result of 8.99. However, when I use the equation in Javascript I mysteriously get 6.33
The actual equation looks like
VO2move = VO2rest+(((C1*g2)+VO2walkmin)+(1+(C2*g2))*(C3*s2^2))*t2;
but I removed all the variables in an attempt to debug (I thought it might be some error where I needed parseInt)
Here are the whole functions for reference
function calc(){
var temp = 0;
var total = 0;
for(i = 0; i<sArr.length; i++){
total = total + calc2(i);
}
var o = document.getElementById("output");
o.value = total;
}
function calc2(i){
var s = document.getElementById("s"+i);
var g = document.getElementById("g"+i);
var t = document.getElementById("t"+i);
var VO2walkmin = 3.28;
var VO2rest = 3.05;
var C1 = 0.32;
var C2 = 0.19;
var C3 = 2.66;
var Cdecline = 0.73;
var s2 = s.value;
var g2 = g.value;
var t2 = t.value;
var negGrade = g.value;
if(g2 < 0){g2 = 0};
//VO2move = ((C1 * g2)+VO2walkmin)+((1+(C2*g2))*(C3*s2^2)); //ORIGINAL TRANSCRIPTION
//VO2move = VO2rest+(((C1*g2)+VO2walkmin)+(1+(C2*g2))*(C3*s2^2))*t2; // TRANSLATED FROM COPY PASTE
VO2move = 3.05+(((0.32*0)+3.28)+(1+(0.19*0))*(2.66*1^2))*1; // COPY - PASTED FROM EXCEL
return VO2move;
}
Even naked numbers I still get the output of 6.33. I'm totally puzzled, and any help is appreciated.
You need to take the power (exponentiation) operator ** instead of the bitwise XOR operator ^.
console.log(3.05+(((0.32*0)+3.28)+(1+(0.19*0))*(2.66*1**2))*1);
i have a little question:
how i can limit or generate the result of a query in 7 or 8 digits
example:
var x = 3143284294
var y = 387520525892
var z = -7632489234892
var w = 34563
result:
var x = 3143284
var y = 3875205
var z = -763248
var w = 3456300 (fill whit "0")
What function or prefix in javascript will use?
tnks(and sorry for my english)
This converts the number to a string and performs string operations on it. Note that repeat is a fairly recent feature of ECMAScript.
function cutNum(n, limit) {
n = n + '';
n = n.substr(0, limit);
if (n.length < limit) {
n = n + '0'.repeat(limit - n.length);
}
return parseInt(n, 10);
}
var x = 3143284294;
cutNum(x, 7); // 3143284
var z = -7632489234892;
cutNum(z, 7); // -763248
var w = 34563;
cutNum(w, 7); // 3456300
Take a look at the slice() method.
var numbers = "01234567890";
var res = numbers.slice(0,6);
alert(res);
Since your sample also includes that are less than 7 digits, you will want to run a logic check first prior to the slice.
var x = "01"
if(x.length < 7)
x = x + "0000000";
x = x.slice(0,6);
alert(x);
I have made a function but it keeps returning NaN. I can't figure it out why it does this.
function voeruit(){
var invoer1 = 2000;
var invoer2 = 11000;
var invoer3 = 5;
var datum = new Date();
var jaar = datum.getFullYear();
berekenen(invoer1, invoer2, invoer3, jaar);
}
function berekenen(invoer1, invoer2, invoer3, jaar)
{
var leeftijd = jaar - invoer1;
var daling1 = invoer3 / 100;
var daling = 1 - daling;
var totdaling = Math.pow(daling, leeftijd);
var waarde = invoer2 * totdaling;
var uitkomst = waarde;
window.alert(uitkomst);
}
it's a summary where, i think is the problem, so there might be a syntax error.
It's an other language than english, because i'm dutch
Your code has a bug here:
var daling = 1 - daling;
Which should be:
var daling = 1 - daling1;
Looks like you have a typo
var daling1 = invoer3 / 100;
var daling = 1 - daling; //<-- daling1?
Presumably that should be
var daling1 = invoer3 / 100;
var daling = 1 - daling1;
Otherwise you're setting daling to 1 - undefined. Which is indeed not a number.
To able to return something from function you should use
return someValue;
But in your code i could not find something like this. How can you expect function return the value if you dont write return statement?
You are using var daling = 1 - daling; and daling not defined yet, may be you should use daling1
And also I want to suggest to not use variable names which like each other they are always confusing.
im trying to display the 2 decimal point of the 2 total number and minus them but it didnt compute the decimal point. anyone would like to figure this out. thanks.
function calculate() {
var myBox1 = document.getElementById('box1').value;
var myBox2 = document.getElementById('box2').value;
var basicpay = document.getElementById('basicpay');
var myResult = myBox1 * myBox2;
basicpay.value = myResult.toFixed(2);
document.getElementById('both').value = sum() - diff();
}
this is the diff part
function diff() {
var absent = document.getElementById('absent').value;
var tardiness = document.getElementById('tardiness').value;
var sss = document.getElementById('sss').value;
var pagibig = document.getElementById('pagibig').value;
var philhealth = document.getElementById('philhealth').value;
var cashadvances = document.getElementById('cashadvances').value;
var withholdingtax = document.getElementById('withholdingtax').value;
var others = document.getElementById('others').value;
var result =
parseInt(absent) +
parseInt(tardiness) +
parseInt(sss) +
parseInt(pagibig) +
parseInt(philhealth) +
parseInt(cashadvances) +
parseInt(withholdingtax) +
parseInt(others) || 0;
if (!isNaN(result)) {
document.getElementById('totaldeductions').value = result.toFixed(2);
return result;
}
}
this is the sum part
function sum() {
var basicpay = document.getElementById('basicpay').value;
var overtime = document.getElementById('overtime').value;
var regularholiday = document.getElementById('regularholiday').value;
var specialholiday = document.getElementById('specialholiday').value;
var allowanceday = document.getElementById('allowanceday').value;
var monthpay = document.getElementById('monthpay').value;
var others1 = document.getElementById('others1').value;
var result =
parseInt(basicpay) +
parseInt(overtime) +
parseInt(regularholiday) +
parseInt(specialholiday) +
parseInt(allowanceday) +
parseInt(monthpay) +
parseInt(others1) || 0;
if (!isNaN(result)) {
document.getElementById('totalgrosspay').value = result.toFixed(2);
return result;
}
}
In your Sum() and Diff() function, you are working only with integers. Integers are whole numbers only, so will not retain anything after a decimal point. To deal with decimals, you will need to use JavaScript's parseFloat() function. To give an example, in your Sum() function you would change the result calculation to look like the following:
var result =
parseFloat(basicpay) +
parseFloat(overtime) +
parseFloat(regularholiday) +
parseFloat(specialholiday) +
parseFloat(allowanceday) +
parseFloat(monthpay) +
parseFloat(others1) || 0;
This will retain the decimal points in the numbers rather than truncating to whole numbers as the parseInt()
I want to write a function which will allow me to "solve" an equation in js.
what I want (not in a programming language):
function f(x) { 1 + x * x }
var z = 2
var y = f(z) //y will be 5 as a number
what I have written in JS:
function P(cfg) { ....
this.equation = "1 + x";
....};
P.prototype.eqn = function(x) {
var tmp = eval(this.equation);
return tmp;
};
....
P.prototype.draw = function() {....
for(var i = 0; i < z; i++)
ctx.lineTo(i, this.eqn(i));
....};
also I've read that using eval in a loop is probably not a good idea, but I have not figured out another way (yet) (JS beginner)...
The problem with this code is, that at least in FF the var tmp will STILL contain the string from this.equation instead of the calculated value.
I would appreciate any further insight very much!
Thank you for your time :)
EDIT: because my question was not formulated very well:
after the execution of line
var tmp = eval(this.equation);
the var tmp will hold a STRING which equals the string this.equation, instead of the desired solution y value.
Also I do not mean solve but evaluate, thanks for that tip :)
Based on your example, I'd say that you want to "evaluate an expression", rather than "solve an equation". For evaluating an expression, you can probably find many tutorials. I'll break it down in brief though. You need to do a few steps.
Starting with your string "1 + x * x", you need to break it into tokens. Specifically, break it down into: "1", "+", "x", "*", "x". At this point, you can substitute your variables ("x") for their literal values ("2"), giving you "1", "+", "2", "*", "2"
Now you need to parse the expression. Based on order of operations PEMDAS you need to create a tree data structure, where parenthetical clauses (stuff surrounded by parenthesis) are executed first, multiplication and division next, and then additions and subtraction last. Parsing is often not an easy task, and you may want to put together a simpler BNF grammar (though you can probably find a grammar for simple math expressions with some googling).
Next, walk the tree, depth first, evaluating the operations as you go up the tree. Once you get to the top of the tree, you have your solution.
If instead you want to "solve an equation", you're going to need something much more sophisticated, like Sage
I have used this expression evaluator before. It seemed to work very well. It allows you to pass expressions into a Parser that returns a function object that can then evaluate inputs.
var expr = Parser.parse("2 ^ x");
expr.evaluate({ x: 3 }); // 8
It supports trig functions (sin, cos, ect...) and other handy built in functions such as abs & ciel.
var expr = Parser.parse("sin(x/2) + cos(x/2)")
expr.evaluate({x: Math.PI / 2}); // 1
Examples: http://silentmatt.com/javascript-expression-evaluator/
Code: https://github.com/silentmatt/js-expression-eval
Note that this lib does not use eval().
Not sure I entirely understand your question but how about:
var makeFunctionOfX = function(src) {
return Function('x', 'return ' + src);
};
Then you can say things like:
var g = makeFunctionOfX('2 * x')
var y = g(3); // y contains 6
The great advantage of this over eval is that the Function we create has no magic ability to see variables in the scope (hence the need to explicitly pass it x as a parameter name).
Using eval is safe if you trust the input from the user, and works just fine. (I have no idea what you mean by "the var tmp will still have the string this.equation".)
function FuncCreator(eqn){ this.eqn = eqn }
FuncCreator.prototype.run = function(x,y,z){ return eval(this.eqn) }
var add1 = new FuncCreator('1+x');
var result = add1.run(41); // 42
var complex = new FuncCreator('Math.sin(x*y) / Math.cos(z)');
var result = complex.run(3,4,5); // -1.891591285331882
If you don't trust the user input, you'll need to actually parse the input and process it yourself. This is non-trivial.
You can use the expression parser from the math.js library and do something like this:
var parser = math.parser();
var f = parser.eval('function f(x) = 1 + x * x');
// use the created function f in expressions:
parser.eval('z = 2'); // 2
parser.eval('y = f(z)'); // 5
// or use the created function f in JavaScript:
var z = 2; // 2
var y = f(z); // 5
Creating functions in math.js is quite currently limited, loops and blocks needed to define more extensive functions are not yet supported.
This is an old thread, but I wrote this equation calculator, this doesn't solve algebraic equations though. There is however a function that will allow you to provide an array containing assigned variables. But this doesn't solve for variables that don't have an assigned value.
I probably haven't permuted every test case scenario, but it seems to work pretty decent.
Edit: This would have to be modified to handle negative numbers. Other than that... works fine.
Here is a fiddle
<!doctype html>
<html>
<head>
<title>Javascript Equation Calculator</title>
</head>
<body>
<input type="button" onclick="main()" value="calculate"><br>
<input type="text" id="userinput"><br>
<span id="result">Ready.</span><br>
<script>
function Calculator(){}
String.prototype.replaceLast = function (what, replacement)
{
var pcs = this.split(what);
var lastPc = pcs.pop();
return pcs.join(what) + replacement + lastPc;
};
function inS(substr, str){return (str.indexOf(substr) > -1);}
function arrayValueOrToken(arr, key, token)
{
if(key in arr)
{
return arr[key];
}
return token;
}
function reduceEquation(inputStr)
{
console.log("reduceEquation Executed-----");
while(hasNest(inputStr))
{
if(hasNest(inputStr))
{
inputStr = inputStr.replace(")(",')*(');
for(var i=0;i<=9;i++)
{
inputStr = inputStr.replace(i+"(",i+'*(');
inputStr = inputStr.replace(")"+i,')*'+i);
}
var s = inputStr.lastIndexOf("(");
var e = 0;
for(i=s;i,inputStr.length;i++){if(inputStr[i]==")"){e=i+1;break;}}
var eq = inputStr.substring(s,e);
var replace = eq;
eq = eq.replace(/[()]/g, '');
var substitution = solveEquation(eq);
inputStr = inputStr.replaceLast(replace,substitution);
}
}
return inputStr;
}
function solveEquation(eq)
{
console.log("solveEquation Executed-----");
eq = doFirstOrder(eq);
eq = doLastOrder(eq);
return eq;
}
function doFirstOrder(eq)
{
console.log("doFirstOrder Executed-----");
for(var i=0;i<eq.length;i++)
{
if(eq[i]=="*"){eq = solve(eq,"*");return doFirstOrder(eq);}
if(eq[i]=='/'){eq = solve(eq,'/');return doFirstOrder(eq);}
}
return eq;
}
function doLastOrder(eq)
{
console.log("doLastOrder Executed-----");
for(var i=0;i<eq.length;i++)
{
if(eq[i]=="+"){eq = solve(eq,"+");return doLastOrder(eq);}
if(eq[i]=="-"){eq = solve(eq,"-");return doLastOrder(eq);}
}
return eq;
}
function solve(eq, operator)
{
var setOp = operator;
console.log("solve Executed-----");
var buildEq = "",var1 = true,done = false,char="";
var operators = "+-/*";
var ops = operators.replace(operator, '').split('');
var a=ops[0];
var b=ops[1];
var c=ops[2];
for(var i=0;i<eq.length;i++)
{
char = eq[i];
switch(true)
{
case(char==operator):if(var1===true){var1 = false;}else{done = true;}break;
case(char==a):
case(char==b):
case(char==c):if(var1){char = ""; buildEq = "";}else{done = true;}
}
if(done){break;}
buildEq = buildEq + char;
}
var parts = parts = buildEq.split(operator);
var solution = null;
if(operator=="+"){solution = parseFloat(parts[0]) + parseFloat(parts[1]);}
if(operator=="-"){solution = parseFloat(parts[0]) - parseFloat(parts[1]);}
if(operator=="*"){solution = parseFloat(parts[0]) * parseFloat(parts[1]);}
if(operator=="/"){solution = parseFloat(parts[0]) / parseFloat(parts[1]);}
return eq.replace(buildEq, solution);
}
function hasNest(inputStr){return inS("(",inputStr);}
function allNestsComplete(inputStr)
{
var oC = 0, cC = 0,char="";
for(var i=0;i<inputStr.length;i++){char = inputStr[i];if(char=="("){oC+=1;}if(char==")"){cC+=1;}}
return (oC==cC);
}
Calculator.prototype.calc = function(inputStr)
{
console.log("Calc Executed-----");
inputStr = inputStr.replace(/ /g, "");
inputStr = inputStr.replace(/\\/g, '/');
inputStr = inputStr.replace(/x/g, "*")
inputStr = inputStr.replace(/X/g, "*")
if(!allNestsComplete(inputStr)){return "Nested operations not opened/closed properly.";}
inputStr=reduceEquation(inputStr);
inputStr = solveEquation(inputStr);
return inputStr;
};
Calculator.prototype.calcWithVars = function(inputList)
{
if(inputList.length < 2){return "One or more missing arguments!";}
var vars = [];
var assocVars = [];
var lastVarIndex = inputList.length - 2;
var i = 0;
var inputStr = inputList[inputList.length-1];
for(i=0;i<=lastVarIndex;i++)
{
vars.push(inputList[i].replace(/ /g, ""));
}
for(i=0;i<=vars.length-1;i++)
{
var vParts = vars[i].split("=");
var vName = vParts[0];
var vValue = vParts[1];
assocVars[vName] = vValue;
}
inputStr = inputStr.replace(/ /g, "");
var eqVars = inputStr.replace(/\s+/g, ' ').replace(/[^a-zA-Z-]/g, ' ').replace(/\s\s+/g, ' ');
if(inS(" ", eqVars))
{
eqVars = eqVars.split(" ");
}
else{eqVars = [eqVars];}
eqVars.sort(function(a, b){return a.length - a.length;});
var tempTokens = [];
var tempCount = 1;
for(i=0;i<eqVars.length;i++)
{
var eqVname = eqVars[i];
var substitution = arrayValueOrToken(assocVars, eqVname, "<unknown>");
if(substitution != "<unknown>")
{
inputStr = inputStr.replace(eqVname,substitution);
}
else
{
var tempToken = "#______#"+tempCount+"#______#";
tempCount++;
tempTokens.push(tempToken + "?" + eqVname);
inputStr = inputStr.replace(eqVname,tempToken);
}
}
for(i=0;i<tempTokens.length;i++)
{
var tokenSet = tempTokens[i];
var tokenParts = tokenSet.split("?");
var token = tokenParts[0];
var variableName = tokenParts[1];
inputStr = inputStr.replace(token,variableName);
}
var answerName = "<unknown>";
var eq = inputStr;
if(inS("=", inputStr))
{
var eqParts = inputStr.split("=");
answerName = eqParts[0];
eq = eqParts[1];
}
eq = this.calc(eq);
var result = [];
for(i=0;i<eqVars.length;i++)
{
var v = arrayValueOrToken(assocVars, eqVars[i], "<unknown>");
if(v != "<unknown>")
{
result.push(assocVars[eqVars[i]]);
}
}
result.push(eq);
return result;
};
function main()
{
var calculator = new Calculator();
elUserInput = document.getElementById('userinput');
console.log("input: "+ elUserInput.value);
elResult = document.getElementById('result');
equation = elUserInput.value;
result = calculator.calc(equation);
console.log("result: "+ result);
elResult.innerHTML = result;
}
</script>
</body>
</html>