Ask for a html var and pass to JS - javascript

I have created a working Binary to Decimal Calculator but would like a HTML input.
<html>
<input placeholder="00000000" name="htmlinput"></input>
<input id="clickMe" type="button" value="Go" onclick="runbintodec();"></input>
</html>
<script>
function runbintodec()
{
var bin = document.getElementByName('htmlinput').value;
...(Bin to Dec Calc code)
}
</script>
I need some way to take an input from a html input form and send it to the script when i click the button 'go'.

First of all, input is a non-closing tag. Secondly, there's nothing like document.getElementByName, use document.getElementsByName instead or even better - assign an unique id identifier to your input and then catch it by document.getElementById.
function runbintodec() {
var bin = document.getElementsByName('htmlinput')[0].value;
}
<input placeholder="00000000" name="htmlinput">
<input id="clickMe" type="button" value="Go" onclick="runbintodec();">

Related

Cant Get Answer Back In answer Box NAN is being shown

it does not returns prpoer answer it returnes NAN in Answer
<html>
<head>
<script type="text/javascript">
function pro(n,p)
{
var number=parseInt(n);
var powe=parseInt(p);
for(var i=1;i<powe;i++)
{
number*=number;
}
document.getElementById("answer").value=number;
}
</script>
</head>
<body>
<form name="F" >
Enter Number <input type="text" name="num" id="num"/>
Enter Power <select name="powe" id="powe">
<option value="2" >square</option>
<option value="3" >cube</option>
</select>
Answer<input type="text" name="Answer" id="answer" />
<input type="button" onClick="pro(num,powe)" value="Calculate" />
</form>
</body>
</html>
The issue is this: onClick="pro(num,powe)". Instead of the values for num and powe being gotten from the input elements and passed into the pro function, the actual element references (which are not numbers) are being passed.
To solve this problem, you'll need to get the values of the elements. But, before you just make a quick edit to your code, don't use inline HTML event attributes (onclick) in the first place. Instead, separate your JavaScript from your HTML and set up event handlers using modern standards with .addEventListener() as shown below.
Also (FYI):
Since you aren't actually submitting form data anywhere, you don't
need a <form> element.
It's not necessary to use parseInt with p.value because that
value is coming from your select and you've already set those at
whole numbers.
Don't bother with self-terminating tags (<input />) as you
gain nothing from using them.
If you are expecting only numeric input, it's better to use input
type=number which restricts the user input to numbers. Making this change also saves you from worrying about parseInt on the input number being misinterpreted as other bases than 10.
Since you don't want the user to be able to change the result of the
operation, it's better to display it in a non-editable element, like
a span.
It's a good idea to move your <script> element to just before the
closing body tag because, by the time the parser reaches that
point, all your HTML elements will have been parsed into memory.
<html>
<head>
</head>
<body>
<div>
Enter Number <input type="number" name="num" id="num">
</div>
<div>
Enter Power
<select name="powe" id="powe">
<option value="2">square</option>
<option value="3">cube</option>
</select>
</div>
<div>
Answer <span id="answer"></span>
</div>
<div>
<input type="button" value="Calculate">
</div>
<script>
// Get references to the inputs, the answer container and the button
let inputNum = document.getElementById("num");
let power = document.getElementById("powe");
let answer = document.getElementById("answer");
let btn = document.querySelector("input[type='button']");
// Set up the click event handler for the button
btn.addEventListener("click", function(){
// Now you need to get the input values and pass them
// to the function that will act with them
pro(inputNum.value, power.value);
});
function pro(n,p) {
var number = parseInt(n);
for(var i = 1; i < p; i++) {
number *= number;
}
answer.textContent = number;
}
</script>
</body>
</html>
Try
document.getElementById("answer").innerHTML = number

Disappearing HTML - Function

I am trying to make a small calculator-thingy for my website. I want to be able to write a number in a text-input, then get the double of that number back. I tried this way at first:
<form name="form">
<input type="text"/>
</form>
<script type="text/javascript">
function calc() {
var x = document.forms[0].elements[0].value;
document.write(x*2);
}
</script>
<input type="button" onClick="calc()" value="Calculate here"/>
This is working fine, but when calling the function ( calc() ) with the button, all HTML is removed. The only thing appearing is the double of the number (variable x) you wrote. I have read that the "function" make all other HTML disappear.
Is it possible to make the page stay the same, but at the same time showing the calculated number (x*2)? Can I reach the variable x without using a function?
Is it possible to "control" where and how the calculated number (x*2) is going to appear, within the JavaScript or within the HTML?
I am new to this coding art, was hoping to find a relatively easy way to solve this.
Thanks!
The best way is probably to add a div outside the form which is intended to reflect the calculated value. Then you can update calc to find this div and replace its contents with the calculated value.
<script>
function calc() {
var x = document.forms[0].elements[0].value;
var result = x * 2;
document.getElementById("result").innerHTML = result;
}
</script>
<form name="form">
<input type="text"/>
</form>
<input type="button" onclick="calc()" value="Calculate here"/>
<div id="result"></div>
Adding to your original code and the accepted answer.
Make sure that the value you retrieve is an integer(or a float).This way you will prevent the user from getting weird results.
You can do it like this:
<script>
function calc() {
var x = parseFloat(document.forms[0].elements[0].value);// or parseInt(document.forms[0].elements[0].value)
var result = x * 2;
document.getElementById("result").innerHTML = result;
}
</script>
<form name="form">
<input type="text"/>
</form>
<input type="button" onclick="calc()" value="Calculate here"/>
<div id="result"></div>

How can I get the id of a button?

I want to get the #id of an html button, so that I can use it elsewhere.
HTML
<input type="button" onclick="recordToFilename(this);"
id="submitdis" value="Enter Discount Price">
JavaScript
var x = document.getElementById("submitdis");
function recordToFilename(ele) {
console.log(ele.id);
}
Here's my codepen. My goal is to do something similar to this fiddle, but I'm not really sure where to start.
Try this vanilla JS:
var id;
function getId(button){
id = button.id
document.getElementById('output').innerHTML = id;
}
<input type="button" id="button1" onclick="getId(this)" value="Print my ID below.">
<p id="output"></p>
You don't need to get the element by id since you're already passing this in your onclick you have access to it in the function. if you just need the id you can get it by calling getAttribute on the element. Below is an example.
function recordToFilename(el) {
console.log(el.getAttribute('id'));
}
<input type="button" onclick="recordToFilename(this);" id="submitdis" value="Enter Discount Price" />
First you would need to import Jquery inside your html head tag,
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
Then inside your js document this would be your code
$(document).ready(function() {
$('#buttonID').myNewFunc()
}
Let's suppose that on the DOM we have something like this :
<button id="submitdis" class="some-class" >Some Text</button>
to get the id on native JS :
var el = document.getElementById('submitdis');
console.log(el.id) // ===> OUTPUTS 'submitdis'
is that what you're looking for ?`

retrieving text field value using javascript

I want to retrieve textfield value using javascript. suppose i have a code like:
<input type='text' name='txt'>
And I want to retrieve it using javascript. I call a function when a button is clicked:
<input type='button' onclick='retrieve(txt)'>
What coding will the retrieve function consist of?
You can do this:
Markup:
<input type="text" name="txt" id="txt"/>
<input type="button" onclick="retrieve('txt');"/>
JavaScript:
function retrieve(id) {
var txtbox = document.getElementById(id);
var value = txtbox.value;
}
Let's say you have an input on your page with an id of input1, like this:
<input type="text" id="input1" />
You first need to get the element, and if you know the Id, you can use document.getElementById('input1'). Then, just call .value to get the value of the input box:
var value = document.getElementById('input1').value;
Update
Based on your markup, I would suggest specifying an id for your text box. Incase you don't have control over the markup, you can use document.getElementsByName, like so:
var value = document.getElementsByName('txt')[0].value;
One of the way is already explained by Andrew Hare.
You can also do it by entering the value in the textbox and getting a prompt box with entered message when a user click the button.
Let's say, you have a textbox and a input button
<input type="text" name="myText" size="20" />
<input type="button" value="Alert Text" onclick="retrieve()" />
The function for retrieve()
function retrieve()
{
var text = document.simpleForm.myText.value;
alert(text);
}

Calling Javascript from a html form

I am basing my question and example on Jason's answer in this question
I am trying to avoid using an eventListener, and just to call handleClick onsubmit, when the submit button is clicked.
Absolutely nothing happens with the code I have.
Why is handleClick not being called?
<html>
<head>
<script type="text/javascript">
function getRadioButtonValue(rbutton)
{
for (var i = 0; i < rbutton.length; ++i)
{
if (rbutton[i].checked)
return rbutton[i].value;
}
return null;
}
function handleClick(event)
{
alert("Favorite weird creature: "+getRadioButtonValue(this["whichThing"]));
event.preventDefault(); // disable normal form submit behavior
return false; // prevent further bubbling of event
}
</script>
</head>
<body>
<form name="myform" onSubmit="JavaScript:handleClick()">
<input name="Submit" type="submit" value="Update" onClick="JavaScript:handleClick()"/>
Which of the following do you like best?
<p><input type="radio" name="whichThing" value="slithy toves" />Slithy toves</p>
<p><input type="radio" name="whichThing" value="borogoves" />Borogoves</p>
<p><input type="radio" name="whichThing" value="mome raths" />Mome raths</p>
</form>
</body>
</html>
edit:
Please do not suggest a framework as a solution.
Here are the relevant changes I have made to the code, which results in the same behavior.
function handleClick()
{
alert("Favorite weird creature: "+getRadioButtonValue(document.myform['whichThing'])));
event.preventDefault(); // disable normal form submit behavior
return false; // prevent further bubbling of event
}
</script>
</head>
<body>
<form name="aye">;
<input name="Submit" type="submit" value="Update" action="JavaScript:handleClick()"/>
Which of the following do you like best?
<p><input type="radio" name="whichThing" value="slithy toves" />Slithy toves</p>
<p><input type="radio" name="whichThing" value="borogoves" />Borogoves</p>
<p><input type="radio" name="whichThing" value="mome raths" />Mome raths</p>
</form>
You can either use javascript url form with
<form action="javascript:handleClick()">
Or use onSubmit event handler
<form onSubmit="return handleClick()">
In the later form, if you return false from the handleClick it will prevent the normal submision procedure. Return true if you want the browser to follow normal submision procedure.
Your onSubmit event handler in the button also fails because of the Javascript: part
EDIT:
I just tried this code and it works:
<html>
<head>
<script type="text/javascript">
function handleIt() {
alert("hello");
}
</script>
</head>
<body>
<form name="myform" action="javascript:handleIt()">
<input name="Submit" type="submit" value="Update"/>
</form>
</body>
</html>
In this bit of code:
getRadioButtonValue(this["whichThing"]))
you're not actually getting a reference to anything. Therefore, your radiobutton in the getradiobuttonvalue function is undefined and throwing an error.
EDIT
To get the value out of the radio buttons, grab the JQuery library, and then use this:
$('input[name=whichThing]:checked').val()
Edit 2
Due to the desire to reinvent the wheel, here's non-Jquery code:
var t = '';
for (i=0; i<document.myform.whichThing.length; i++) {
if (document.myform.whichThing[i].checked==true) {
t = t + document.myform.whichThing[i].value;
}
}
or, basically, modify the original line of code to read thusly:
getRadioButtonValue(document.myform.whichThing))
Edit 3
Here's your homework:
function handleClick() {
alert("Favorite weird creature: " + getRadioButtonValue(document.aye.whichThing));
//event.preventDefault(); // disable normal form submit behavior
return false; // prevent further bubbling of event
}
</script>
</head>
<body>
<form name="aye" onSubmit="return handleClick()">
<input name="Submit" type="submit" value="Update" />
Which of the following do you like best?
<p><input type="radio" name="whichThing" value="slithy toves" />Slithy toves</p>
<p><input type="radio" name="whichThing" value="borogoves" />Borogoves</p>
<p><input type="radio" name="whichThing" value="mome raths" />Mome raths</p>
</form>
Notice the following, I've moved the function call to the Form's "onSubmit" event. An alternative would be to change your SUBMIT button to a standard button, and put it in the OnClick event for the button. I also removed the unneeded "JavaScript" in front of the function name, and added an explicit RETURN on the value coming out of the function.
In the function itself, I modified the how the form was being accessed. The structure is:
document.[THE FORM NAME].[THE CONTROL NAME] to get at things. Since you renamed your from aye, you had to change the document.myform. to document.aye. Additionally, the document.aye["whichThing"] is just wrong in this context, as it needed to be document.aye.whichThing.
The final bit, was I commented out the event.preventDefault();. that line was not needed for this sample.
EDIT 4 Just to be clear. document.aye["whichThing"] will provide you direct access to the selected value, but document.aye.whichThing gets you access to the collection of radio buttons which you then need to check. Since you're using the "getRadioButtonValue(object)" function to iterate through the collection, you need to use document.aye.whichThing.
See the difference in this method:
function handleClick() {
alert("Direct Access: " + document.aye["whichThing"]);
alert("Favorite weird creature: " + getRadioButtonValue(document.aye.whichThing));
return false; // prevent further bubbling of event
}
Pretty example by Miquel (#32) should be refilled:
<html>
<head>
<script type="text/javascript">
function handleIt(txt) { // txt == content of form input
alert("Entered value: " + txt);
}
</script>
</head>
<body>
<!-- javascript function in form action must have a parameter. This
parameter contains a value of named input -->
<form name="myform" action="javascript:handleIt(lastname.value)">
<input type="text" name="lastname" id="lastname" maxlength="40">
<input name="Submit" type="submit" value="Update"/>
</form>
</body>
</html>
And the form should have:
<form name="myform" action="javascript:handleIt(lastname.value)">
There are a few things to change in your edited version:
You've taken the suggestion of using document.myform['whichThing'] a bit too literally. Your form is named "aye", so the code to access the whichThing radio buttons should use that name: `document.aye['whichThing'].
There's no such thing as an action attribute for the <input> tag. Use onclick instead: <input name="Submit" type="submit" value="Update" onclick="handleClick();return false"/>
Obtaining and cancelling an Event object in a browser is a very involved process. It varies a lot by browser type and version. IE and Firefox handle these things very differently, so a simple event.preventDefault() won't work... in fact, the event variable probably won't even be defined because this is an onclick handler from a tag. This is why Stephen above is trying so hard to suggest a framework. I realize you want to know the mechanics, and I recommend google for that. In this case, as a simple workaround, use return false in the onclick tag as in number 2 above (or return false from the function as stephen suggested).
Because of #3, get rid of everything not the alert statement in your handler.
The code should now look like:
function handleClick()
{
alert("Favorite weird creature: "+getRadioButtonValue(document.aye['whichThing']));
}
</script>
</head>
<body>
<form name="aye">
<input name="Submit" type="submit" value="Update" onclick="handleClick();return false"/>
Which of the following do you like best?
<p><input type="radio" name="whichThing" value="slithy toves" />Slithy toves</p>
<p><input type="radio" name="whichThing" value="borogoves" />Borogoves</p>
<p><input type="radio" name="whichThing" value="mome raths" />Mome raths</p>
</form>
Everything seems to be perfect in your code except the fact that handleClick() isn't working because this function lacks a parameter in its function call invocation(but the function definition within has an argument which makes a function mismatch to occur).
The following is a sample working code for calculating all semester's total marks and corresponding grade. It demonstrates the use of a JavaScript function(call) within a html file and also solves the problem you are facing.
<!DOCTYPE html>
<html>
<head>
<title> Semester Results </title>
</head>
<body>
<h1> Semester Marks </h1> <br>
<script type = "text/javascript">
function checkMarks(total)
{
document.write("<h1> Final Result !!! </h1><br>");
document.write("Total Marks = " + total + "<br><br>");
var avg = total / 6.0;
document.write("CGPA = " + (avg / 10.0).toFixed(2) + "<br><br>");
if(avg >= 90)
document.write("Grade = A");
else if(avg >= 80)
document.write("Grade = B");
else if(avg >= 70)
document.write("Grade = C");
else if(avg >= 60)
document.write("Grade = D");
else if(avg >= 50)
document.write("Grade = Pass");
else
document.write("Grade = Fail");
}
</script>
<form name = "myform" action = "javascript:checkMarks(Number(s1.value) + Number(s2.value) + Number(s3.value) + Number(s4.value) + Number(s5.value) + Number(s6.value))"/>
Semester 1: <input type = "text" id = "s1"/> <br><br>
Semester 2: <input type = "text" id = "s2"/> <br><br>
Semester 3: <input type = "text" id = "s3"/> <br><br>
Semester 4: <input type = "text" id = "s4"/> <br><br>
Semester 5: <input type = "text" id = "s5"/> <br><br>
Semester 6: <input type = "text" id = "s6"/> <br><br><br>
<input type = "submit" value = "Submit"/>
</form>
</body>
</html>
Remove javascript: from onclick=".., onsubmit=".. declarations
javascript: prefix is used only in href="" or similar attributes (not events related)

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