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Dear all,
it's my simple JS program.
I can't figure out that why can't i stop the loop by using "guess==null".
Please help!!
var target = prompt("Please enter a number small than 50:");
var guess = "";
var time = 0;
do{
guess = prompt("Please Guess:");
if(guess == target || guess == null){
break;
}
if(guess < target){
alert("bigger!");
time++;
continue;
}else{
alert("smaller!");
time++;
continue;
}
}while(true)
if(guess==null){
document.write("the answer is:"+target);
}else{
document.write("Good!共猜了:"+(time+1));
}
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Try using the isNaN[^] function - i.e.:
isNaN(guess)
rather than
guess == null
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 really useful! thanks a lot!
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guess can return an empty string when you click on Ok without entering anything, guess will only be null if you click on cancel or if you close the prompt.
Add guess == '' to your if statement or replace guess == null with isNaN(guess) that will check if the value is a legal number
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 really useful! thanks a lot!
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A few things that might be helpful.
You don't really need to test for the 'break' options (as your code appears) if you
do something like this:
do {
if(something is true) {
do-this;
}
else
if(something else is true) {
do this;
}
. . . etc . . .
else
break;
} while(true)
This style will handle anything 'unexpected' - that is, anything you didn't intend
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "As far as we know, our computer has never had an undetected error." - Weisert | | "If you are searching for perfection in others, then you seek disappointment. If you are seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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 really useful! thanks a lot!
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/*
Dear all,
<script>
function Array2D(x,y){
this.length = x*y;
this.x = x;
this.y = y;
for(var i=0 ; i<this.length ; i++){
this[i] = null;
}
this.get = function(x,y){
return this[x*this.x+y];
}
this.set = function(x,y,value){
this[x*this.x+y] = value;
}
}
</script>
<script>
var a2d = Array2D(10,10);
a2d.set(2,3,"2");
alert(this.get(1,2));
</script>
Uncaught TypeError: Cannot read property 'set' of undefined
How does it happen?and what should i do to avoid this?
*/
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It's undefined because you ahven't returned anything form your Array2D function. Try adding
return this;
at the end of it.
Also, your
alert(this.get(1,2));
shouold be
alert(a2d.get(1,2));
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thanks a lot! it works! 
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I need to check whether control id is available or visible (whether it is defined or undefined). how to check this process in javascript. any example pls
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This code will check if an element exits with that ID:
if(document.getElementById(id)!=null)
{
}
You can use JQuery to check if the element is visible:
$('#MyID').is(':visible')
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function validate()
{
var dd = document.frmreq;
if (mailid.value == "")
{ alert ("Pls enter mailid"); return false;
}
if (dd.description.value == "")
{
return false;
}
return true;
}
mailid and mobileno is get from DB
here, i can't able to get the mailid and mobileno for validation. any one explain me the problem here.
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Use the getElementById method[^] to access the elements:
function validate()
{
var mailid = document.getElementById("mailid");
if (mailid.value === "")
{
alert("Please enter mailid");
mailid.focus();
return false;
}
var description = document.getElementById("description");
if (description.value === "")
{
alert("Please enter description");
description.focus();
return false;
}
return true;
}
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Just taking my first javascript coding class and having a hard time with understanding all of it. Wanted to know what the main difference is in for and while loops and when it's best to use either one? Also want to know what the difference is between document.write and getElementById? Does it matter which one to use for output?
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Member 11972043 wrote: Wanted to know what the main difference is in for and while loops and when it's best to use either one?
This is not something unique to JavaScript so I suggest you google for vs while loops and you'll see the difference. There's a subtle difference and most often depends on your preference to which one you use. W3Schools.com is a good resource. For example, see http://www.w3schools.com/js/js_loop_while.asp[^]
Member 11972043 wrote: Also want to know what the difference is between document.write and getElementById?
These cannot be compared to each other. document.write does what it sounds like. It calls the write method on the document. The document is the webpage so this can be used to write something on the page. I suggest not using it because you won't control, very well, where the output is. It's much better to put output into a control so that you can style it, position it, etc.
That's where getElementById comes in. It also does as it's name implies. It gets an element on your webpage by passing in the id of that element.
So, for example, if you wanted to do some output you could do something like this:
document.getElementById("myText").value = "Some Text";
Again, W3Schools.com, http://www.w3schools.com/jsref/met_doc_getelementbyid.asp[^]
There are only 10 types of people in the world, those who understand binary and those who don't.
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The main difference between for and while is that (if you know how these conditional statements will work).
for is used to do a definite number of task i.e you know the limit for the process, say you want to print the number of anything in an array,etc.you can use counter to proceed further.
less interaction between user and machine.
while is same as for in some cases,you when the process will end but still in places like getting an input from the user which decides when the end should occur you have go with while.you can use you counters as well as boolean values.
i.e you can ask the user to whether continue or break after every successful process.interaction between the user and machine .
getelementbyid is used to get an input to a variable by using an id attribute from tag.
write is used to output the values assigned to it.
instead of this you can you use console.log().
sorry if it wasn't helpful because i'm new.
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How can I add an image with a submit button but still show the words submit?
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Hello. I have been asked to build a cross-browser extension, and I have never built one before. I wondered, firstly, what sort of timeframe I should be looking at, and secondly, what sort of fee? I am also new to contract work, having left the industry as a data harvester and junior developer for self-employment, just a few months ago. Should I be charging per hour, or a flat fee for such a project?
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We can't really answer that question for you. We have no idea what the extension is supposed to do, what skills you have, how quickly you can pick up new skills if needed, or how quickly you can work. We also have no idea whether your client would accept an open-ended hourly rate, or expects you to quote and charge a fixed fee.
If you charge a fixed fee and it doesn't completely cover your time, will you gain anything? Will you learn additional skills that you can use in future projects? Will you generate good-will with the customer, and potentially get extra work or referrals from them in the future?
Coming up with accurate estimates is hard enough for our own work; it's virtually impossible for someone else's! 
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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sir i want the image to be dispalyed in a browser when we choose the image from the option choose file and click on submit .I wrote the code as below
Quote: <html>
<body>
Please enter your details for our Dating Website!
<form action="https://amazonstore.com" method="POST">
Your Face
<label for="image">Your Image</label>
<input type="file" name="FileToUpload" value="ChooseFile" required>
<label for="preview">Image Preview: </label></label>
Quote: </form>
<input type="submit" name="submit" value="submit" align=="center">
</form>
</body>
</html>
modified 8-Oct-15 10:26am.
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42 - it's the answer to everything.
Now try actually asking a question.
Remember, we can't see your screen, access your computer, or read your mind, so you need to explain what the problem is as if we don't know what you're talking about (because we don't).
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Hi,
i am fairly new to programming.
i am making a website where the front page is simply an image, think google with just a picture in the center.
however there is no search bar no nothing, only the witty and curious enough to click the image will get login/register buttons where they can further click them to enter user pass email information
so far i have something like this
which i want to redirect to a function
var spawnButtons=function(){
that ultimately makes the login/register buttons/links whatever you call them appear which then go on to make the username/password/email appear/disappear depending on which login or register is clicked which could then be safely entered(i'm assuming some sort of php)}
i hope for this to all be on the same page for aesthetic purposes but if not i can understand. so everything is hidden essentially until it is clicked.
thanks.
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Peter Roman wrote: <img src="D:/Pictures/JIT.png" width="347" height ="176" />
You can't use local paths to display an image on a website. You need to use a URL, either absolute (src="http://yoursite/pictures/jit.png"), relative to the current site (src="/pictures/jit.png"), or relative to the current page (src="pictures/jit.png").
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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