Programming Forums - Help with Calculator

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Help with Calculator

I currently am making a calculator (to learn javascript better)

it's a karvonen heart rate calculator which calculates what your target heart rate BPM should be for a percentage workout, the formula is as follows:

(maximum heart rate = maximum achievable heart rate)
(minimum heart rate = heart rate measured just after waking up)

maximum heart rate - minimum heart rate * workout percentage + minimum heart rate = target bpm

ok, now i can get the formula kinda working.. the poblem i have is with this code:

targetHeartRateLow=Math.floor((maxHeartRate-minHeartRate)*percentZoneMin/100)+minHeartRate;

instead of adding minHeartRate it joins it like two strings like 4499 instead of showing 143 (44+99). Below is the code i'm using

function calc(form){

var maxHeartRate;

var minHeartRate;

var percentZoneMin;

var percentZoneMax;

var targetHeartRateLow;

var targetHeartRateHigh;



minHeartRate=form.rest_hr.value;

maxHeartRate=form.max_hr.value;

percentZoneMin=form.percent_zone1.value;

percentZoneMax=form.percent_zone2.value;



targetHeartRateLow=Math.floor((maxHeartRate-minHeartRate)*percentZoneMin/100)+minHeartRate;

targetHeartRateHigh=Math.floor((maxHeartRate-minHeartRate)*percentZoneMax/100)+minHeartRate;

form.target_hr1.value=targetHeartRateLow;

form.target_hr2.value=targetHeartRateHigh;



}

look into using the parseInt function.
(http://www.w3schools.com/jsref/jsref_parseInt.asp)

it's been a while since i last posted (been busy) but i got it in the end, here is the code i used.

//Work Out Heart Rate Min - Max
function calc(form){
var maxHeartRate;
var minHeartRate;
var percentZoneMin;
var percentZoneMax;
var targetHeartRateLow;
var targetHeartRateHigh;
//Get form values
minHeartRate=parseInt(form.rest_hr.value,10);
maxHeartRate=parseInt(form.max_hr.value,10);
percentZoneMin=form.percent_zone1.value;
percentZoneMax=form.percent_zone2.value;
//Run our calculation
targetHeartRateLow=Math.floor((maxHeartRate-minHeartRate)*percentZoneMin/100)+minHeartRate;
targetHeartRateHigh=Math.floor((maxHeartRate-minHeartRate)*percentZoneMax/100)+minHeartRate;
//update our form
form.target_hr1.value=targetHeartRateLow;
form.target_hr2.value=targetHeartRateHigh;
 
}

Thanks for the help.

I know it's over, but you could also use the Number() function as well as the parseInt() function. ;)
It brings back a float / double.