I have JavaScript code and below line has problem.
if ((hr==20)) document.write("Good Night"); document.getElementById('Night).style.display=''
ERROR
Uncaught TypeError: Cannot read property 'style' of null at Column 69
My div tag details are:
<div id="Night" style="display: none;">
<img src="Img/night.png" style="position: fixed; top: 0px; left: 5%; height: auto; width: 100%; z-index: -2147483640;">
<img src="Img/moon.gif" style="position: fixed; top: 0px; left: 5%; height: 100%; width: auto; z-index: -2147483639;"></div>
Complete JavaScript:
<script language="JavaScript">
<!--
document.write("<dl><dd>")
day = new Date()
hr = day.getHours()
if ((hr==1)||(hr==2)||(hr==3)||(hr==4) || (hr==5)) document.write("Should not you be sleeping?")
if ((hr==6) || (hr==7) || (hr==8) || (hr==9) || (hr==10) || (hr==11)) document.write("Good Morning!")
if ((hr==12)) document.write("Let's have lunch?")
if ((hr==13) || (hr==14) || (hr==15) || (hr==16) || (hr==17)) document.write("Good afternoon!")
if ((hr==18) || (hr==19)) document.write("Good late afternoon!")
if ((hr==20)) document.write("Good Night"); document.getElementById('Night').style.display=''
if ((hr==21)) document.write("Good Night"); document.getElementById('Night').style.display='none'
if ((hr==22)) document.write("Good Night")
if (hr==23) document.write("Oh My! It's almost midnight!")
if (hr==0) document.write("Midnight!<br>It is already tomorrow!") document.write("</dl>")
//--->
</script>
Can someone help me?
The "Cannot read property 'click' of null" error occurs when trying to call the click method on a null value. To solve the error, run the JS script after the DOM elements are available and make sure you only call the method on valid DOM elements.
This error TypeError: document. getelementbyid(...) is null would seem to indicate that there is no such element with an ID passed to getElementById() exist. This can happen if the JavaScript code is executed before the page is fully loaded, so its not able to find the element.
What Causes TypeError: Cannot Read Property of Undefined. Undefined means that a variable has been declared but has not been assigned a value. In JavaScript, properties and functions can only belong to objects.
In your script, this part:
document.getElementById('Noite')
must be returning null
and you are also attempting to set the display
property to an invalid value. There are a couple of possible reasons for this first part to be null
.
You are running the script too early before the document has been loaded and thus the Noite
item can't be found.
There is no Noite
item in your HTML.
I should point out that your use of document.write()
in this case code probably signifies a problem. If the document has already loaded, then a new document.write()
will clear the old content and start a new fresh document so no Noite
item would be found.
If your document has not yet been loaded and thus you're doing document.write()
inline to add HTML inline to the current document, then your document has not yet been fully loaded so that's probably why it can't find the Noite
item.
The solution is probably to put this part of your script at the very end of your document so everything before it has already been loaded. So move this to the end of your body:
document.getElementById('Noite').style.display='block';
And, make sure that there are no document.write()
statements in javascript after the document has been loaded (because they will clear the previous document and start a new one).
In addition, setting the display
property to "display"
doesn't make sense to me. The valid options for that are "block"
, "inline"
, "none"
, "table"
, etc... I'm not aware of any option named "display"
for that style property. See here for valid options for teh display
property.
You can see the fixed code work here in this demo: http://jsfiddle.net/jfriend00/yVJY4/. That jsFiddle is configured to have the javascript placed at the end of the document body so it runs after the document has been loaded.
P.S. I should point out that your lack of braces for your if
statements and your inclusion of multiple statements on the same line makes your code very misleading and unclear.
I'm having a really hard time figuring out what you're asking, but here's a cleaned up version of your code that works which you can also see working here: http://jsfiddle.net/jfriend00/QCxwr/. Here's a list of the changes I made:
var
declarations to your variables (a good habit to always use).if
statement was changed into an if/else which is a lot more efficient and more self-documenting as to what you're doing.if
statement so it absolutely clear which statements are part of the if/else
and which are not.</dd>
tag you were inserting.style.display = '';
to style.display = 'block';
.The code:
<div id="Night" style="display: none;">
<img src="Img/night.png" style="position: fixed; top: 0px; left: 5%; height: auto; width: 100%; z-index: -2147483640;">
<img src="Img/moon.gif" style="position: fixed; top: 0px; left: 5%; height: 100%; width: auto; z-index: -2147483639;">
</div>
<script>
document.write("<dl><dd>");
var day = new Date();
var hr = day.getHours();
if (hr == 0) {
document.write("Meia-noite!<br>Já é amanhã!");
} else if (hr <=5 ) {
document.write(" Você não<br> devia<br> estar<br>dormindo?");
} else if (hr <= 11) {
document.write("Bom dia!");
} else if (hr == 12) {
document.write(" Vamos<br> almoçar?");
} else if (hr <= 17) {
document.write("Boa Tarde");
} else if (hr <= 19) {
document.write(" Bom final<br> de tarde!");
} else if (hr == 20) {
document.write(" Boa Noite");
document.getElementById('Noite').style.display='block';
} else if (hr == 21) {
document.write(" Boa Noite");
document.getElementById('Noite').style.display='none';
} else if (hr == 22) {
document.write(" Boa Noite");
} else if (hr == 23) {
document.write("Ó Meu! Já é quase meia-noite!");
}
document.write("</dl></dd>");
</script>
This happens because document.write
would overwrite your existing code therefore place your div
before your javascript code. e.g.:
CSS:
#mydiv {
visibility:hidden;
}
Inside your html file
<div id="mydiv">
<p>Hello world</p>
</div>
<script type="text/javascript">
document.getElementById('mydiv').style.visibility='visible';
</script>
Hope this was helpful
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