js method to implement text box to support addition and subtraction operations

js method to implement text box to support addition and subtraction operations_javascript skills

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Release： 2016-05-16 15:44:18

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The example in this article describes how js implements text boxes to support addition and subtraction operations. Share it with everyone for your reference. The details are as follows:

This is a web form effect that allows the text box in the form to support addition and subtraction operations. However, you have to enter the correct calculation formula, otherwise it is not so smart. For example, if you enter 1 5, the calculation will be displayed next to the text box. As a result, this is possible thanks to the power of JavaScript.

The screenshot of the running effect is as follows:

The online demo address is as follows:

http://demo.jb51.net/js/2015/js-math-input-method-codes/

The specific code is as follows:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>支持加减运算的文本框</title>
<meta http-equiv="content-type" content="text/html;charset=gb2312">
<style type="text/css">
body{color:#000;font-size:14px;font-family:Verdana,Arial,Helvetica,sans-serif,"宋体";}
input{border-style:solid;border-color:#868275;background-color:#f9f9f9;border-width:1px;color:#505050;vertical-align:middle;}
</style>
<script language=javascript>
function FloatAdd(arg1,arg2){
 var r1,r2,m;
 try{r1=arg1.toString().split(".")[1].length}catch(e){r1=0}
 try{r2=arg2.toString().split(".")[1].length}catch(e){r2=0}
 m=Math.pow(10,Math.max(r1,r2))
 return (arg1*m+arg2*m)/m
}
function FloatSubtr(arg1,arg2){
 return FloatAdd(arg1,-arg2);
}
function IsMoney(Money){
 if(/^[\d|+|.|-]+$/.test(Money)) return true;
 return false;
}
function result(){
 str=document.getElementById("buy").value;
 if(!(IsMoney(str))){
  document.getElementById("amount").innerHTML ="无效金额";
  return false;
 }
 var len=str.length,money=0,Num=0;
 var NumStr="",ctrlflag="x",cflag=0;
 for(var i=0;i<len; i++){
  c= str.charAt(i);
  if((c=="+")||(c=="-")){
   if(i+1<len){
    if ((str.charAt(i+1)=="+")||(str.charAt(i+1)=="-")) continue;
   }
   if((NumStr!="")&&(isNaN(NumStr))){
    if(isNaN(NumStr)){
     document.getElementById("amount").innerHTML ="输入无效金额";
     return false;
    }
   }
   if(NumStr!=""){
   //alert("i："+i+"NumStr:"+NumStr);
    if ((ctrlflag=="+")||(ctrlflag=="x")){
     Num=parseFloat(NumStr);
     //alert(ctrlflag+"money："+money+"Num："+Num);
     money=FloatAdd(money,Num);
     NumStr="";
     Num=0;
     ctrlflag=c;
    }
    else{
     //alert(money+"里面减了"+NumStr);
     Num=parseFloat(NumStr);
     money=FloatSubtr(money,Num);
     NumStr="";
     Num=0;
     ctrlflag=c;
    }
   }
   else{
    ctrlflag=c;
   }
  continue;
  }
  else{
   NumStr=NumStr+""+c;
  }
 }
 if((NumStr!="")&&(isNaN(NumStr))){
  if (isNaN(NumStr)){
   document.getElementById("amount").innerHTML ="无效金额"+NumStr;
   return false;
  }
 }
 if((ctrlflag=="-")&&(NumStr!="")){
  Num=parseFloat(NumStr); 
  money=FloatSubtr(money,Num);
 }
 if(((ctrlflag=="+")||(ctrlflag=="x"))&&((NumStr!=""))){
  Num=parseFloat(NumStr);
  money=FloatAdd(money,Num);
 }
 document.getElementById("amount").innerHTML =money;
}
</script>
</head>
<body>
请输入加减计算式：<input id="buy" name="buy" maxlength="30" type="text" onkeyup="javascript:result();">
<span id="amount"></span>
</body>
</html>

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I hope this article will be helpful to everyone’s JavaScript programming design.