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Body Mass Calculator

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The final step is to install the Javascript that does the actual calculations for the body fat calculator. All you need to do is to copy the following code and save it as bmicalc.js.

// Body Mass Index Calculator
// copyright 28th April 2006, by Stephen Chapman
// permission to use this Javascript on your web page is granted
// provided that all of the code in this script (including these
// comments) is used without any alteration
function valButton(btn) {var cnt = -1;for (var i=btn.length-1; i > -1; i--) {   if (btn[i].checked) {cnt = i; i = -1;}}if (cnt > -1) return btn[cnt].value;else return null;}function stripBlanks(fld) {var result = "";var c = 0;for (i=0; i < fld.length; i++) {if (fld.charAt(i) != " " || c > 0) {result += fld.charAt(i);if (fld.charAt(i) != " ") c = result.length;}}return result.substr(0,c);}function calc(thisform) {var d = valButton(thisform.d);if (d == null) {alert("You must choose centimetres/kg or inches/lb");return false;}cv = d.split(',');;var h = stripBlanks(thisform.h.value);if (h == '') {alert("You must enter your height");thisform.h.focus();return false;}if (h != Number(h) || (h = Number(h*cv[0]/100)) < 1 || h > 2.5) {alert("Invalid height entered");thisform.h.focus();return false;}var w = stripBlanks(thisform.w.value);if (w == '') {alert("You must enter your weight");thisform.w.focus();return false;}if (w != Number(w) || (w = Number(w/cv[1])) < 25 || w > 250) {alert("Invalid weight entered");thisform.w.focus();return false;} thisform.f.value = Math.round(w / (h*h)*100)/100;}

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Guide since 2004

Stephen Chapman
JavaScript Guide

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