Buggy Javascript PDF -

i working on pdf custom calculations.

below part of code giving me various issues:

var widowervalue = getfield("widowerallow").value;   var widoweranswer = getfield("widowsenti").value;   var widowerchildren = getfield("under18total01").value;    var child01benefit = widowerchildren * 1620;   var child01allowance = widowerchildren * 1534;     if(widoweranswer == "yes"){     if(child01benefit != 0 && child01allowance !=0){     event.value = widowervalue + child01benefit + child01allowance;     }else{       event.value = widowervalue;     }    }   else if(widoweranswer == "no"){     if(child01benefit !=0){       event.value = child01benefit;       }   }  

this in textfield values change dependent on conditions met. works(sometimes), have click box , delete wrong value entered , show correct calculation. other times doesn't add values joins them e.g instead of 5 + 5 = 10(correct) place 5+5 = 55(wrong), again corrected when manually remove wrong value.

can offer insight why happening?

thanks

in js + operator concat strings , addition of integer.

string + string string concatination. number + number addition of numbers.

var string = '5';    function concat() {    document.getelementbyid("result").innerhtml = string + string;  }    function addition() {    document.getelementbyid("result").innerhtml = number(string) + number(string);  }

<div id='result'>click button</div>  <button onclick="concat();">string concat</button>  <button onclick="addition();">addition</button>