I am absolutely new to javascript. I am trying to create my first html page and add some javascript on my html tags. I want to have two boxes where I can input any number and click on Show me! in order to get the result. I wrote the code below but is doesn't do anything:
<!DOCTYPE html>
<html>
<head>
<title>Interactive JS homework</title>
<style>
</style>
<script>
function calculate(){
var a = parseFloat(document.getElementById("a").value);
var b = parseFloat(document.getElementById("b").value);
document.getElementById("result") == a+b;
}
</script>
</head>
<body>
<form>
<p>
<input type="text" id="a" oninput="calculate();">
<input type="text" id="b" oninput="calculate();">
<input type="button" id="showme" value="Show me!" onclick="calculate();">
<input type="text" id="result">
</p>
</form>
</body>
Any help with where I am wrong?
Many thanks in advance!
You have to use the value property of the element. Please notice the changes in the operator used, it should be assignment (=) not compariosn (==).
document.getElementById("result").value = a+b;
I will also suggest you to assign 0 when there is no value in the element. This will prevent showing unexpected NaN as result if any of the element's value is empty.
<!DOCTYPE html>
<html>
<head>
<title>Interactive JS homework</title>
<style>
</style>
<script>
function calculate(){
var val1 = document.getElementById("a").value.trim();
var val2 = document.getElementById("b").value.trim();
var a = parseFloat(val1 == ""? 0 : val1);
var b = parseFloat(val2 == ""? 0 : val2);
document.getElementById("result").value = a+b;
}
</script>
</head>
<body>
<form>
<p>
<input type="text" id="a" oninput="calculate();">
<input type="text" id="b" oninput="calculate();">
<input type="button" id="showme" value="Show me!" onclick="calculate();">
<input type="text" id="result">
</p>
</form>
</body>
Well, it seems you merely forgot a little thing.
When reading the values of the a and b text boxes, you correctly used .value after retrieving the elements to access their value, but when you tried to set the value of result text box, you instead just compared it to the value of a+b. The == operator is for comparison, not setting a value.
Just as well, you will need to set the .value of the result text box, instead of the text box itself.
<!DOCTYPE html>
<html>
<head>
<title>Interactive JS homework</title>
<style>
</style>
<script>
function calculate(){
var a = parseFloat(document.getElementById("a").value);
var b = parseFloat(document.getElementById("b").value);
document.getElementById("result").value = a+b;
}
</script>
</head>
<body>
<form>
<p>
<input type="text" id="a" oninput="calculate();">
<input type="text" id="b" oninput="calculate();">
<input type="button" id="showme" value="Show me!" onclick="calculate();">
<input type="text" id="result">
</p>
</form>
</body>
Related
When I'm running this code it is not showing me the message which I want to display (i.e: res).Suppose I'm giving an input "$code$".Can anyone just help me out?
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
<h1>Enter a sample message</h1>
<form>
<input type="text" name="a" id="a">
<button onclick="parse()">submit</button>
<p id="a"></p>
</form>
<script>
function parse(){
var msg=document.getElementById("a").innerHTML;
var res=msg.replace("$code$","1101");
document.getElementById("a").innerHTML=res;//this is to print res.
}
</script>
</body>
</html>
Two elements can't have the same ID. Further, an input element's value can not be obtained using the innerHTML property. Also, on clicking the submit button, the page will reload since the form get's submitted. To prevent that, call the function parse in an onsubmit on the <form> tag, and return false from the function.
<!DOCTYPE HTML>
<html>
<head>
</head>
<body>
<h1>Enter a sample message</h1>
<form onsubmit="return parse();">
<input type="text" name="a" id="a">
<button type="submit">submit</button>
<p id="b"></p>
</form>
<script>
function parse(){
var msg = document.getElementById("a").value;
document.getElementById("b").innerHTML = msg;
return false;
}
</script>
</body>
</html>
Check this:
<form>
<input type="text" name="a" class="input_field" id="a">
<button type="button" onclick="parse()">submit</button>
<p id="a"></p>
</form>
<script>
function parse(){
var msg=document.getElementById("a").innerHTML;
var form = document.getElementsByTagName("form")[0]
msg = form.getElementsByClassName("input_field")[0].value;//this is to print res.
}
</script>
I added type="button" to the button to prevent the form from reloading the page
I am getting back into javascript for a job I am going to start soon. for some reason i forgot how to do a simple calculator. I dont understand why my even onclick is null when it is a button. I am sure this is a very simple answer I just cant see it.
if(document.getElementById("add").onclick == true){
alert("hey");}
<!DOCTYPE html>
<html>
<head>
<title>TEST</title>
<script src= "script.js"> </script>
</head>
<body>
<h3> Calculator: </h3>
<input type="text" name="a">
<input type="text" name="b">
<input type="button" value="+" name="add">
</body>
</html>
To get you started I made minor changes to your code, go through the changes and understand the use of each change.
function sum(){
var a = document.getElementById("a");
var b = document.getElementById("b");
alert(Number(a.value) + Number(b.value));
}
<!DOCTYPE html>
<html>
<head>
<title>TEST</title>
<script src= "script.js"> </script>
</head>
<body>
<h3> Calculator: </h3>
<input type="text" name="a" id="a">
<input type="text" name="b" id="b">
<input type="button" onClick="sum()" value="+" name="add">
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<title>Function</title>
<script type="text/javascript">
function sum(x,y) {
var z = x+y;
document.write("Sum is"+z);
}
</script>
</head>
<body>
<form>
<input type="" id="t1" name=""/>
<input type="" id="t2" name=""/>
<input type="button" onclick="sum(t1.value,t2.value)" value="Click me"/>
</form>
</body>
</html>
Hi Guys, I am a beginner with JavaScript and I'm facing this little problem. If I enter 5 and 5 the result is 55. But I want to sum up these values.
As #TonyDong said, uses parseInt to convert the string to int if desired input is integer.
To make your function works better, you need to validate the inputs first before sum.
Below is one example:
make the type of two inputs are 'number'
checkValidity() for the form or two inputs in function=sum. if validated, sum the values, if not, return error.
<!DOCTYPE html>
<html>
<head>
<title>Function</title>
<script type="text/javascript">
function sum(x,y)
{
if(document.getElementById("submit").checkValidity()) {
var z = parseInt(x)+parseInt(y);
document.write("Sum is "+z);
}
else {
document.write("Input value must be Int!");
}
}
</script>
</head>
<body>
<form id="submit">
<input id="t1" name="" type="number"/>
<input id="t2" name="" type="number"/>
<input type="button" onclick="sum(t1.value,t2.value)" value="Click me"/>
</form>
</body>
</html>
You should covert x and y to integers first, like parseInt(x) and parseInt(y) while doing the summation.
Then, instead of document.write, you can use console.log.
<!DOCTYPE html>
<html>
<head>
<title>Function</title>
<script type="text/javascript">
function sum(x,y) {
var z = parseInt(x)+parseInt(y);
console.log("Sum is",z);
}
</script>
</head>
<body>
<form>
<input type="" id="t1" name=""/>
<input type="" id="t2" name=""/>
<input type="button" onclick="sum(t1.value,t2.value)" value="Click me"/>
</form>
</body>
</html>
Hi so yes this is a previous issue i have had, i have hit the books and whent back to basics adjusted a few things but im still having trouble getting the input value to push to the array can some one please help me get my head around this thanks
<!DOCTYPE html>
<html>
<body>
<script type="text/javascript">
var number=["1"]
function myFunction()
{
var x=document.getElementById("box");
number.push=document.getElementById("input").value;
x.innerHTML=number.join('<br/>');
}
</script>
<form>
<input id="input" type=text>
<input type=button onclick="myFunction()" value="Add Number"/>
</form>
<div id="box"; style="border:1px solid black;width:150px;height:150px;overflow:auto">
</div>
</body>
</html>
Here is the mistake:
number.push(document.getElementById("input").value);
push is a method, not an attribute ;-)
JSFiddle
PS: Why the ; after id="box"; ? You should fix that too..! ;-)
You were close, here's the working code:
<!DOCTYPE html>
<html>
<body>
<script type="text/javascript">
var number = [];
function myFunction()
{
var x = document.getElementById("box");
number.push(document.getElementById("input").value);
x.innerHTML = number.join('<br/>');
}
</script>
<form>
<input id="input" type=text>
<input type=button onclick="myFunction()" value="Add Number"/>
</form>
<div id="box" style="border:1px solid black;width:150px;height:150px;overflow:auto">
</div>
</body>
</html>
I want the text to be printed without commas.
<html>
<head>
<title>Reverse</title>
</head>
<body>
<form name="rev">
Enter the string : <input type="text" name="str"/>
<input type="button" value="click" onclick="rev1()" /><br>
reverse of given string : <input type="text" name="res"/>
</form>
<script type="text/JavaScript">
function rev1(){
var a=rev.str.value;
var b=[];
var i,j=0;
for(i=a.length-1;i>=0;i--){
b[j]=a[i];
j++
}
//rev.res.value=b;
alert(b);
}
</script>
</body>
</html>
If I give the input as abc I am getting an output as c,b,a, but I want it as cba.
Try this:
alert( b.join("") )
You could also reverse a string more easily by:
"hello".split("").reverse().join("")
//"olleh"
You may reverse your string using javascript built-in functions:
<html>
<head>
<title>Reverse</title>
</head>
<body>
<form name="rev">
Enter the string : <input type="text" name="str"/>
<input type="button" value="click" onclick="rev1()" /><br>
reverse of given string : <input type="text" name="res"/>
</form>
<script type="text/JavaScript">
function rev1(){
var a=rev.str.value;
var b=a.split("").reverse().join("");
//rev.res.value=b;
alert(b);
}
</script>
</body>
</html>
You may also transfer join your array elements to become a string
<html>
<head>
<title>Reverse</title>
</head>
<body>
<form name="rev">
Enter the string : <input type="text" name="str"/>
<input type="button" value="click" onclick="rev1()" /><br>
reverse of given string : <input type="text" name="res"/>
</form>
<script type="text/JavaScript">
function rev1(){
var a=rev.str.value;
var b=[];
var i,j=0;
for(i=a.length-1;i>=0;i--){
b[j]=a[i];
j++
}
//rev.res.value=b;
alert(b.join(""));
}
</script>
</body>
</html>
You can also use document.getElementById().value.reverse().join("");