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问题:

I was just trying to write a simple javascript program that will demonstrate to take user input from text field, and clicking the button will display the summation result of those number in another text field. But unfortunately the below code is not working. I am totally clueless in doing this. Clicking the button does not show anything in the result text field.

Please help.

<body>
    <div>
        <div>
            <h1>Add two number using text box as input using javascript</h1>
        </div>
            Enter First Number : <br>
            <input type="text" id="Text1" name="TextBox1">
            <br>
            Enter Second Number : <br>
            <input type="text" id="Text2" name="TextBox2">
            <br>
            Result : <br>
            <input type="text" id="txtresult" name="TextBox3">
            <br>
         <input type="button" name="clickbtn" value="Display Result" onclick="add_number()">

        <script type="text/javascript">
            function add_number(){
            var first_number = parseInt(document.getElementsById("Text1").value);
            var second_number = parseInt(document.getElementsById("Text2").value);
            var result = first_number + second_number;
            document.getElementById("txtresult").innerHTML = result;    
            }
        </script>

回答1:

Here a working fiddle: http://jsfiddle.net/sjh36otu/

        function add_number() {

            var first_number = parseInt(document.getElementById("Text1").value);
            var second_number = parseInt(document.getElementById("Text2").value);
            var result = first_number + second_number;

            document.getElementById("txtresult").value = result;
        }

回答2:

When you assign your variables "first_number" and "second_number", you need to change "document.getElementsById" to the singular "document.getElementById".

回答3:

var first_number = parseInt(document.getElementById("Text1").value);
var second_number = parseInt(document.getElementById("Text2").value);

// This is because your method .getElementById has the letter 's': .getElement**s**ById

回答4:

<script>

function sum()
{
    var value1= parseInt(document.getElementById("txtfirst").value);
    var value2=parseInt(document.getElementById("txtsecond").value);
    var sum=value1+value2;
    document.getElementById("result").value=sum;

}
 </script>

回答5:

You made a simple mistake. Don't worry.... Simply use getElementById instead getElementsById

true

var first_number = parseInt(document.getElementById("Text1").value);

False

var first_number = parseInt(document.getElementsById("Text1").value);

Thanks ...

回答6:

var app = angular.module('myApp', []);
app.controller('myCtrl', function($scope) {

    $scope.minus = function() {     

	    var a = Number($scope.a || 0);
            var b = Number($scope.b || 0);
            $scope.sum1 = a-b;
	   // $scope.sum = $scope.sum1+1; 
	   alert($scope.sum1);
    }

   $scope.add = function() {     

	    var c = Number($scope.c || 0);
            var d = Number($scope.d || 0);
            $scope.sum2 = c+d;
	   alert($scope.sum2);
    }
});

<head>
      <script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.3.3/angular.min.js"></script>
   </head>
<body>

<div ng-app="myApp" ng-controller="myCtrl">
     <h3>Using Double Negation</h3>

    <p>First Number:
        <input type="text" ng-model="a" />
    </p>
    <p>Second Number:
        <input type="text" ng-model="b" />
    </p>
    <button id="minus" ng-click="minus()">Minus</button>
    <!-- <p>Sum: {{ a - b }}</p>  -->
 <p>Sum: {{ sum1 }}</p>

    <p>First Number:
        <input type="number" ng-model="c" />
    </p>
    <p>Second Number:
        <input type="number" ng-model="d" />
    </p>
 <button id="minus" ng-click="add()">Add</button>
    <p>Sum: {{ sum2 }}</p>
</div>