JS: ReferenceError: function is not defined - javascript

When my HTML file is loaded, it automatically shows a "login window" (see the function draw_login). When I click on the generated button I get the following error:
ReferenceError: emit_login is not defined
window.onload = function() {
var socket = io();
draw_login ();
function emit_login() {
var login_name = document.getElementById("login_name").value;
var login_password = document.getElementById("login_password").value;
socket.emit('login', {
name:"",
pw:""
});
}
function draw_login() {
document.getElementById("status_bar").innerHTML =
'Name:<input type="text" id="login_name"></input><br>'+
'Password:<input type="password" id="login_password"></input><br>'+
'<button type="button" onclick="emit_login();">login</button>';
}
}
Has anyone an idea or some suggestions?
Thanks in advance!

As Daniel A. White said;
Move it outside of the onload function.
And as Amit said, if you want to learn about why you need to do this, you should read about scopes in JavaScript as this is what causes your error. The function emit_login is created inside of the anonymous function window.onload, which means that anything outside of window.onload will not have access to anything outside of this.
Please correct me if I said anything wrong here. Haven't used JS for quite some time.

It looks like you are receiving this error because you have the emit_login function being called from your click handler which does not share the same scope as the function being called in your onload.
https://jsfiddle.net/sL7e5cut/
function emit_login() {
var login_name = document.getElementById("login_name").value;
var login_password = document.getElementById("login_password").value;
alert('login', {
name:"",
pw:""
});
}
(function() {
draw_login ();
function draw_login() {
document.body.innerHTML =
'Name:<input type="text" id="login_name"></input><br>'+
'Password:<input type="password" id="login_password"></input><br>'+
'<button type="button" onclick="emit_login();">login</button>';
}
}())
try defining the emit_login function outside the onload handler, and everything should work fine.

Keeping things out of the global scope is a good thing, but when you combine it with inline eventlisteners, e.g onclick="emit_login()" it just doesn't work.
Instead of having an inline eventlistener, you can do something like this in draw_login:
function draw_login() {
document.getElementById("status_bar").innerHTML =
'Name:<input type="text" id="login_name"></input><br>'+
'Password:<input type="password" id="login_password"></input><br>'+
'<button type="button">login</button>';
document
.querySelector('#status_bar button')
.addEventListener('click', emit_login, false);
}
Update: The whole point being that using the onclick attribute is discouraged, and definitely not one of the good parts of javascript.

Related

Call a function outside of ViewModel scope

I have the following code outside the scope of my view model and i am attempting to call it with a click binding.
function Policy(data) {
var self = this;
Object.keys(data).forEach(function(prop) {
self[prop] = data[prop];
});
var generate = function() {
console.log("test");
// window.open("www.google.com")
// window.open("{{ url_for('genreport') }}/" + qvm.letter() + '/' + self.id);
}
}
however, when i try to call the function i get that generate is not defined. the code for my binding is below
<button class="btn btn-lg btn-primary btn-block" data-bind="click: function(){ generate() }">Generate</button>
I have tried calling Policy.generate, $data.generate, and i cannot get this function to call.
I know this issue is simple and im probably missing something that should be smashing me in the face but i'm oblivious, any help would be appreciated.
The fix was just to place the said function within the scope of my ViewModel, it is now fixed.
You have declared generate using a local variable. It is not visible outside the scope of Policy. If you want to create Policy.generate, you should do that:
Policy.generate = function () {

Input's value as variable is not defined

Got an input type text. Whatever entered is supposed to become a value for variable, and further on from there. Yet, i get error "Uncaught ReferenceError: emailvar is not defined" and the whole script breaks from there.
html
<input type="text" class="signfield emfield" />
<div class="submt sbmtfrm" href="#" style="cursor:pointer;">Step 2</div>
and js
$(".sbmtfrm").click(function(){
var emailvar = $(".emfield").val();
});
In your code, emailvar is being defined in a function closure, and only that function has access to it.
$(".sbmtfrm").click(function(){
var emailvar = $(".emfield").val();
});
If you want to use emailvar outside of your jQuery event handler, you will need to first define it (not assign it, yet) outside the scope of the function.
(function(window, $) { // closure
var emailvar;
$(".sbmtfrm").click(function() {
emailvar = $(".emfield").val();
});
// you now have access to `emailvar` in any function in this closure
}(window, jQuery));
You need to declare emailvar as a global variable to use it outside of that click event handler:
$(function()
{
var emailvar;
$(".sbmtfrm").click(function()
{
emailvar = $(".emfield").val();
});
function foo()
{
console.log(emailvar);
}
}

How do I make my click catcher work?

I'm trying to create a simple click catcher where if you click .image-class the javascript will take the href from another element with a class name of .btn and send you to it's destination. Though I keep getting errors on lines 7 & 10 saying that undefined is not a function. How do I make this work?
<script>
var ClickCatcher=
{
init:function(){
var link = jQuery('.btn')[1].href;
var imgCatch = jQuery('.image-class');
imgCatch.addEventListener("click", ClickCatcher.clickListener, false);
},
clickListener:function(){
window.location = link;
}
};
ClickCatcher.init();
</script>
You can do this with jquery with a simple click event
jQuery('.image-class').on('click', function (){
window.location = jQuery('.btn').eq(1).attr('href');
});
But if you still want to write in the way you have you can do:
var ClickCatcher = {
init: function () {
jQuery('.image-class').on('click', function (){
window.location = jQuery('.btn').eq(1).attr('href');
});
}
};
ClickCatcher.init();
Just make sure to fire the init method after dom load.
update: One issue with it is that you have coded your target etc in the code rather then pass it, so its going to be hard to reuse, you'd be better off doing:
var ClickCatcher = {
init: function ($button, loc) {
$button.on('click', function (){
window.location = loc;
});
}
};
ClickCatcher.init(jQuery('.image-class'), jQuery('.btn').eq(1).attr('href'));
That way the internal working is seperate from the dom (as you are passing the dom dependencies to the function.
#atmd showed a very good way of doing this. If you just want to know what your mistake was though. It is wa an error in your jQuery stament to get the btn href
jQuery('.btn')[1].href
you need to call the attr function and then get the href attr. and use .eq(1) to reduce the set to the first btn
jQuery('.btn').eq(1).attr('href);

Calling a function from an html document will not generate an alert

Hi all thanks for taking a look.
I am trying to call a javascript function when I click on the update button.
Here is the javascript
var text2Array = function() {
// takes the value from the text area and loads it to the array variable.
alert("test");
}
and the html
<button id="update" onclick="text2Array()">Update</button>
if you would like to see all the code check out this jsfiddle
http://jsfiddle.net/runningman24/wAPNU/24/
I have tried to make the function global, no luck, I can get the alert to work from the html, but for some reason it won't call the function???
You have an error in the declaration of the pswdBld function in your JavaScript.
...
var pswdBld() = function() {
---^^---
...
This is causing a syntax error and avoiding the load of your JavaScript file.
See the corrected version.
Also, you may consider binding the event and not inlining it.
<button id="update">Update</button>
var on = function(e, types, fn) {
if (e.addEventListener) {
e.addEventListener(types, fn, false);
} else {
e.attachEvent('on' + types, fn);
}
};
on(document.getElementById("update"), "click", text2Array);​
See it live.
In your fiddle, in the drop-down in the top left, change "onLoad" to "no wrap (head)"
Then change
var text2Array = function()
var pswdBld() = function()
to
function text2Array()
function pswdBld()
and it will alert as expected.
You have a syntax error in the line below..
var pswdBld() = function
^--- Remove this
supposed to be
var pswdBld = function
Also make sure you are calling this script just at the end of the body tag..
Because you are using Function Expressions and not Function Declaration
var pwsdBld = function() // Function Expression
function pwsdBld() // Function Declaration
Check Fiddle

Javascript , event handler is always called, even if the event is not raised

i have the following code which extends the JQuery and adds a method to the JQuery:
$.fn.attachWithMessage = function () {
$(this).focusin(showMessage());
}
function showMessage() {
alert('hi');
}
so I can use that code as follows :
<input type="text" name="name" id="textbox" />
$(document).ready(function () {
$("#textbox").attachWithMessage ();
});
when I load the page for the first time, a message box shows up with ('hi') message.
even if I didn't click in the text box.
I also tried the click event, and the message still shows automatically.
any ideas ??
The issue here is that when you pass showMessage() as a parameter to focusin, the function showMessage is executed and the return value is passed to focusin.
Instead you need to pass a reference to the function (without the paranthesis).
Use the following code to extend:
$.fn.attachWithMessage = function () {
$(this).focusin(showMessage);
}
Working example# http://jsfiddle.net/eXEP5/
EDIT:
If you want to pass a parameter to showMessage then try this:
$.fn.attachWithMessage = function () {
var param1 = "Some Param";
$(this).focusin(function(){
showMessage(param1); //Make sure showMessage is modified accordingly for the parameters.
});
}
just remove the parenthesis
$(this).focusin(showMessage());
should be
$(this).focusin(showMessage);
Hope this helps

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