As below you can see I want perform calculation of adding and subtracting but the program not giving output of calculation. there is input box for operator 1 and operator 2. I create two function add and sub. And using document.getElementById I pass the value of a and b and want to calculate but the function is does not giving output.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
Operator1:<input type="text" id="a">
<br><br>
Operator2:<input type="text" id="b">
<br><br>
<input type="button" value="Add" id="add" onclick="addd()">
<input type="button" value="sub" id="sub" onclick="subb()">
<br><br>
Result: <input type="text" id="res">
<script>
function addd(){
var ra= document.getElementById('a').value;
var rb=document.getElementById('b').value;
var rab=ra rb;
Document.getElementById('res').value==rab;
}
function subb(){
var ra= document.getElementById('a').value;
var rb=document.getElementById('b').value;
var rab=ra-rb;
document.getElementById('res').value==rab;
}
</script>
</body>
</html>CodePudding user response：
You want to make sure you're using the assignment operator, instead of the comparison operator.
Try document.getElementById('res').value = rab; instead.
CodePudding user response：
I'll provide an example that you'll hopefully learn from, but I really recommend you go and learn the basics before you continue programming.
<!DOCTYPE html>
<html>
<head>
<style>input[type=number], button { display:inline-block; margin-bottom: 4px; }</style>
</head>
<body>
<input type="number" id="input-a">
<input type="number" id="input-b"><br>
<button type="button" id="add">Add</button>
<button type="button" id="subtract">Subtract</button><br>
<input type="number" id="result" disabled>
<script>
const resultElement = document.querySelector("#result");
const inputAElement = document.querySelector("#input-a");
const inputBElement = document.querySelector("#input-b");
document.querySelector("#add").addEventListener("click", event => {
resultElement.value = inputAElement.value inputBElement.value;
});
document.querySelector("#subtract").addEventListener("click", event => {
resultElement.value = inputAElement.value - inputBElement.value;
});
</script>
</body>
</html>
The only thing that's not self-explanatory here is the actual calculation. Notice how I put a at the start of each value inputAElement.value? That's to cast the value to a number for the calculation. Otherwise in certain situations, the value could be treated as a text value and just mashed together (e.g. 5 1 = 51).
Use CSS styles to change the look, as shown in the style tag. Abusing won't make you any friends.
<!DOCTYPE html>
<html>
<head>
<style>input[type=number], button { display:inline-block; margin-bottom: 4px; }</style>
</head>
<body>
<input type="number" id="input-a">
<input type="number" id="input-b"><br>
<button type="button" id="add">Add</button>
<button type="button" id="subtract">Subtract</button><br>
<input type="number" id="result" disabled>
<script>
const resultElement = document.querySelector("#result");
const inputAElement = document.querySelector("#input-a");
const inputBElement = document.querySelector("#input-b");
document.querySelector("#add").addEventListener("click", event => {
resultElement.value = inputAElement.value inputBElement.value;
});
document.querySelector("#subtract").addEventListener("click", event => {
resultElement.value = inputAElement.value - inputBElement.value;
});
</script>
</body>
</html>