javascript - Simple math but its not working? -

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i have table users can enter part number, part price , quantity. multiple's price , quantity total. got part , running.

now have taxes on part , grand total im getting:

function calculateit() {     var mybox1 = $( 'input[name=tax2]:checked' ).val(); //taxes value     var mybox2 = document.getelementbyid('partstotalvalue').value; //parts total value     var result = document.getelementbyid('partstax'); // input field total of taxes * parts     var myresult = mybox1 * mybox2; //result = taxes * parts total     result.value = myresult; // display results      var result2 = document.getelementbyid('partstotalwithtax');  // inputp field taxes + total value     var totalresult = myresult + mybox2; // totalresult = taxes on part + parts total     result2.value = totalresult; // display results } 

here's fiddle:

https://jsfiddle.net/jdarville/hxqev0be/

problem + operator , variable types.

in case try add string

var = "1" + "2"; <- 12 

what need use parsefloat , math

var = parsefloat("2") + parsefloat("2.14") <- 4.14 

hope helps.