i build a calc & want to a review that what i did wrong & what is right method to do.    <html>  <script>        var inputIdFirst = valueOfX,inputIdSecond = valueOfY,outputId = resultHere;    var getInputs = function(id) {      return parseInt(document.getElementById(id).value);    }    var showOutput = function(outputValue, outputIdAsArg) {      //if no argument is given then by default outputId taken      document.getElementById(outputId).innerHTML = outputValue;    }    var manuplateAs = function(operationName, valueOfX, valueOfY) {      if(operationName == 'add')        return valueOfX + valueOfY;      else if(operationName == 'sub')        return valueOfX - valueOfY;      else if(operationName == 'mul')        return valueOfX * valueOfY;      else if(operationName == 'div')        return valueOfX / valueOfY;      //can add as many as you wish     }     var operation = function(operationName){      x = getInputs(inputIdFirst);      y = getInputs(inputIdSecond);      output = manuplateAs(operationName, x, y);      showOutput(output);      console.log(x +   + operationName +   + y +  =  + output)      //see console to understand this more      console.log(this)    };  </script></head><body>      Enter first number      <input type=number id=valueOfX>      Enter second number      <input type=number id=valueOfY>      <button onclick=operation('add')> Add </button>      <button onclick=operation('sub')> Sub</button>      <button onclick=operation('mul')> Mult</button>      <button onclick=operation('div')> Divi</button>      <h1 id=resultHere></h1></body></html>
JavaScript calculator with two inputs and four operations
javascript;html;calculator