I made a button click counter for a website using some JavaScript.
The counter works well, but now I'm stuck in making the saving of the count. You know, if I click the button 3 times, the text says 3 Times. But I want to save that value so if the user refreshes the page, it should display 3 Times again.
I knew of using localStorage, I followed a simple tutorial and applied it to my code, but it does not seem to be working. When I run the page in Microsoft Edge and see the Debug page (F12), the console throws an error that says: Unable to get property 'getItem' of undefined or null reference. I searched in other posts but no one of these could solve my problem. It seems to be stuck when retrieving the value in localStorage.
This is my code:
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Increment count when button is clicked</title>
</head>
<body>
<input type="button" value="Registrar" id="countButton" />
<input id="ocityField" type="text" value="" placeholder="Ciudad de Origen"/>
<input id="cityField" type="text" value="" placeholder="Ciudad de participación"/>
<input id="name" type="text" value="" placeholder="Nombre"/>
<p>Personas Registradas: <span id="displayCount">0</span></p>
<script type="text/javascript">
var count = 0;
var button = document.getElementById("countButton");
var display = document.getElementById("displayCount");
var textbox = document.getElementById("ocityField");
var textboxa = document.getElementById("cityField");
var textboxb = document.getElementById("name");
if(window.localStorage.getItem('count')){
var savedcount = window.localStorage.getItem('count');
count = window.localStorage.getItem('count');
}else{
count = 0;
}
display.innerHTML = count;
button.onclick = function(){
var mystring = textbox.value;
var mystring2 = textboxa.value;
var mystring3 = textboxb.value;
if(!mystring.match(/\S/) || !mystring2.match(/\S/) || !mystring3.match(/\S/)) {
alert ('Empty value is not allowed');
return false;
} else {
count++;
window.localStorage.setItem('count', count);
display.innerHTML = count;
textbox.value = "";
textboxa.value = "";
textboxb.value = "";
return true;
}
}
</script>
</body>
</html>
I tried using window.localStorage and just localStorage but no one did work.
May be that you use the IE browser does not support localStorage，The code can run in Chrome49.
Can I Use localStorage, here you can check what browser supports localStorage with version numbers.
Alternate way to store data on client side is cookies if localStorage doesn't supported by browser.
You can also use third party plugins like Modernizer, to check whether browser supports or not.
Modernizr.localstorage if it evaluate to true the browser supports localStorage.
Following example demonstrates localStorage and cookies depending on browser compatibility. uses Modernizer and jQuery
codepen
Related
Edit: Just confirming: I want what the user typed to be saved so that when he reloads/leaves the webpage and comes back what he wrote earlier is still there.
I tried using cookies but it only put one line of Default(variable) when I reloaded the page. Im trying to get it to work with localStorage now but it sets the textarea to "[object HTMLTextAreaElement]" or blank when I reload. I read that this error can be caused by forgetting to add the .value after getElementById() but I did not make this mistake. I am hosting and testing the webpage on Github(pages). What am I doing wrong? here is the code(ignore the comments also it might not work in jsfiddle bc it localstorage didn't work there for me):
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>le epic web page</title>
</head>
<body><!--
= "\n"-->
<textarea id="txt" rows="4" cols="50" oninput="save();"></textarea>
<script>
var Default="P1 Homework: \nP2 Homework: \nP3 Homework: \nP4 Homework: \n";
if(localStorage.getItem("P") == ""){
document.getElementById("txt").value=Default;
localStorage.setItem("P")=Default;
}else{
document.getElementById("txt").value=localStorage.getItem("P");
}
//update cookie (called when typed)
function save(){
var txt=document.getElementById("txt").value;
//txt=txt.replace(/\r\n|\r|\n/g,"</br>");
localStorage.setItem("P",txt);//set cookie to innerHTML of textArea, expires in 1 day
}
//when page closed/reloaded
window.onbeforeunload = function(){
localStorage.setItem("P",txt);//update cookie when page is closed https://stackoverflow.com/a/13443562
}
</script>
</body>
</html>
When you are exiting the page, you are referencing the text element and storing that in localstorage. Since localStorage is a string it converts the html element reference into the text you see.
window.onbeforeunload = function(){
localStorage.setItem("P",txt);
}
You are doing it correctly with save, so just call save with the beforeunload event
window.addEventListener('beforeunload', save);
Another bug in the code is the line
if(localStorage.getItem("P") == ""){
when localStorage is not set, it returns null. So the check would need to be a truthy check ( or you can check for nullv)
if(!localStorage.getItem("P")){
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>le epic web page</title>
</head>
<body>
<textarea id="txt" rows="4" cols="50" oninput="save();"></textarea>
</body>
<script>
const Default =
"P1 Homework: \nP2 Homework: \nP3 Homework: \nP4 Homework: \n";
if (
localStorage.getItem("P") === "" ||
localStorage.getItem("P") === null ||
localStorage.getItem("P") === undefined
) {
localStorage.setItem("P", Default);
} else {
let currentValue = document.getElementById("txt");
currentValue.value = localStorage.getItem("P");
}
function save() {
let txt = document.getElementById("txt").value;
localStorage.setItem("P", txt);
}
window.onbeforeunload = function () {
let txt = document.getElementById("txt").value;
localStorage.setItem("P", txt);
};
</script>
</html>
I want to make a counter remains dynamic and non-bootable when updating
web page,
here is my code the problem is that when I refresh the page the counter(setTimeout) will count again from zero to 5 I want it to count from the last value before
the refresh
<html>
<head>
<meta charset="utf-8"/>
<title>Insert title here</title>
</head>
<script type="text/javascript">
setTimeout(function(){document.getElementById("tm").style.display='block'},
5000);
</script>
<body>
<form id="customer" action="/htmlvalidation" method="post">
<div>
<label>Time</label>
<input id="tm" type="text" style="display: none;"/>
</div>
<div>
<button type="submit">Add Customer</button>
</div>
</form>
</body>
</html>
thank you
You will have to manually store the counter value in the client's browser; by default, browsers will not retain any of a webpage's state when it is closed (or refreshed). For example, you may use the localStorage API:
const STORAGE_KEY = 'counter';
const TARGET_ELEMENT_ID = 'counter-div';
const INTERVAL = 1000;
const INC = 1;
// Notice the '+' below to make sure val is a number.
let val = +localStorage.getItem(STORAGE_KEY) || 0;
document.getElementById(TARGET_ELEMENT_ID).innerHTML = val;
setInterval(() => {
val += INC;
localStorage.setItem(STORAGE_KEY, val);
document.getElementById(TARGET_ELEMENT_ID).innerHTML = val;
}, INTERVAL);
Here is a working example on codepen (it seems stackoverflow's snippets do not support localStorage).
(I didn't use your snippet because I wasn't sure what you were trying to do).
You could store the last timer iteration using localStorage before the user closes or navigates away from the tab, and resume when needed.
More about localStorage
Is it possible to pass the totalScore var to another page onclick so that it can be displayed there? ex: click submit link it goes to yourscore.html and display the score on page
$("#process").click(function() {
var totalScore = 0;
$(".targetKeep").each( function(i, tK) {
if (typeof($(tK).raty('score')) != "undefined") {
totalScore += $(tK).raty('score');
}
});
alert("Total Score = "+totalScore);
});
Let we suppose that your HTML may be as follows:
<!DOCTYPE html>
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("#process").click(function() {
var totalScore = 0;
/*
Your code to calculate Total Score
Remove the next line in real code.
*/
totalScore = 55; //Remove this
alert("Total Score = "+totalScore);
$("#submit-link").attr('href',"http://example.com/yourscore.html?totalScore="+totalScore);
});
});
</script>
<meta charset=utf-8 />
<title>JS Bin</title>
</head>
<body>
<button id="process">Process</button>
<br />
Submit Total Score
</body>
</html>
Check out this DEMO
In yourscore.html you may able to know more in the following queation to extract the URL parameter from the URL:
Parse URL with jquery/ javascript?
This is generally done by changing the url of the page. i.e. if you are going go to a new page, just do:
http://example.com/new/page?param1=test
If the page already exists in a new window (like a popup that you own), set the url to something new:
http://example.com/new/page#param
Open a window:
var win = window.open('http://example.com/new/page?totalscore'+totalscore,'window');
Change the location:
win.location.href='http://example.com/new/page?totalscore'+totalscore;
Other ways of doing this could be websockets or cookies or localstorage in HTML5.
if you are aiming to support more modern browsers the elegant solution could be to use sessionStorage or localStorage! Its extremely simple and can be cleared and set as you need it. The maximum size at the low end is 2mb but if your only storing INTs then you should be okay.
DOCS:
http://www.html5rocks.com/en/features/storage
http://dev.w3.org/html5/webstorage/
DEMO:
http://html5demos.com/storage
EXAMPLE:
addEvent(document.querySelector('#local'), 'keyup', function () {
localStorage.setItem('value', this.value);
localStorage.setItem('timestamp', (new Date()).getTime());
//GO TO YOUR NEXT PAGEHERE
});
I need to POST form values from one page to another using Javascript.
Now, I know that I could use a server-side technology like ASP.Net or PHP to post values but I am not allowed to use any server side script.
I am aware that using the GET method, I can pass the form values as a query string but the values will not be passed securely (which is an important requirement!)
The conditions listed below:
This code should take the values that are posted to the page and
repost to target page. HTTP POST only (not get).
In no cases, even error, the request should not stop on this bridge page.
The script needs to handle multiple posted values.
Try to use standard javascript (no 3rd party library)
Script needs to work in IE, FF, Safari, most standard browsers
Can anyone please help me find a solution to this or point me to some resource that will help me find the soln? Thanks in advance. Below is the code for passing values as a query string. Can I modify this so that my above requirements are satisfied?
FORM
<html>
<head>
<title>Test</title>
<script type="text/javascript">
function goto_page(page) {
var usbnum = document.getElementById('usbnum').value;
var usbcode = document.getElementById('usbcode').value;
var q_str = '?usbnum=' + usbnum + '&usbcode=' + usbcode;
var url = page + q_str;
window.location = url;
}
</script>
</head>
<form id="form1" method="post">
<div>
USB No: <input name="usbnum" id="usbnum" type="text" size="80" /><br />
USB Code: <input name="usbcode" id="usbcode" type="text" size="80"/>
</div>
Next
</form>
</body>
</html>
BRIDGE PAGE
<html>
<head>
<title>Bridge Page</title>
<script type="text/javascript">
function get_params() {
var url = window.location.href;
var q_str_part = url.match(/\?(.+)$/)[1];
var val_pairs = q_str_part.split('&');
var params = {};
for (var i = 0; i < val_pairs.length; i++) {
var tmp = val_pairs[i].split('=');
params[tmp[0]] = typeof tmp[1] != 'undefined' ? tmp[1] : '';
}
return params;
}
function write_params() {
var params = get_params();
var txt = 'Hello ';
for (var i in params) {
txt += params[i] + ' ';
}
var body = document.getElementsByTagName('body')[0];
body.innerHTML += txt;
}
function write_params() {
var params = get_params();
var num_container = document.getElementById('usbnum');
var code_container = document.getElementById('usbcode');
num_container.innerHTML = params.usbnum;
code_container.innerHTML = params.usbcode;
}
</script>
</head>
<body onLoad="write_params()">
</body>
</html>
POST data can only be handled by server side code. There is no way you can use them in your javascript without help from a server side code.
You can only use GET or you can think about cookies. But at other hand, why do you want to change current page?! you can use AJAX to load more data without refreshing and no need of posting or getting variables.
I have my website
www.aplicatii-iphone.ro
and another
page.html on localhost
<html>
<head>
<title>Object References across Iframes</title>
<script type="text/javascript">
window.onload = function(){
var form = document.getElementById('testForm');
form.testBtn.onclick = sendData;
}
function notify() {
//alert('iframe loaded');
var iframeEl = document.getElementById('ifrm');
if ( iframeEl && iframeEl.parentNode && document.createElement ) {
var newTxt = document.createTextNode('The iframe has loaded and your browser supports it\'s onload attribute.');
var newPara = document.createElement("p");
newPara.className = 'demo';
newPara.appendChild(newTxt);
iframeEl.parentNode.insertBefore(newPara, iframeEl);
}
}
function sendData() { // to form inside iframed document
// frames array method:
// window.frames['ifrm'].document.forms['ifrmTest'].elements['display'].value = this.form.testEntry.value;
var ifrm = document.getElementById('ifrm');
var doc = ifrm.contentDocument? ifrm.contentDocument: ifrm.contentWindow.document;
var form = doc.getElementById('search-input'); // <------<< search input
form.display.value = this.form.testEntry.value;
form.submit();
}
// test in iframed doc
var counter = 0;
</script>
</head>
<body>
<form id="testForm" action="#">
<p><input type="text" name="testEntry" size="30" value="[enter something]" /> <input name="testBtn" type="button" value="Click Me" /></p>
</form>
<iframe name="ifrm" id="ifrm" src="http://www.aplicatii-iphone.ro" onload="notify()" width="900">Sorry, your browser doesn't support iframes.</iframe>
</body>
</html>
And every time I press the button Click Me, I want that the state of www.aplicatii-iphone.ro to be like a user searched for that value written in "testEntry" from outside of the iframe.
I tried something there ... but I can't figure it out ... any help please?
I took the example from here http://www.dyn-web.com/tutorials/iframes/refs.php
If you know you're using a modern browser, you could use postMessage to communicate between the frames. Here's a good write-up: http://ajaxian.com/archives/cross-window-messaging-with-html-5-postmessage
If you need to support legacy browsers, you could use Google Closure's CrossPageChannel object to communicate between frames.
Unfortunatly, this is not possible due to the Same orgin policy.
And changing the document.domain-value only helps if you try to connect a subdomain with the main-domain.
Edit
If you avoid the same-orgin-problem by using a page on the same website, this should work for you:
window.frames['ifrm'].document.getElementById("search-input").value = document.getElementsByName("testEntry")[0].value;
window.frames['ifrm'].document.getElementById("cse-search-box").submit();