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Error in if/while (condition) {: missing Value where TRUE/FALSE needed
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The evaluation of condition resulted in an NA. The if conditional must have either a TRUE or FALSE result.
if (NA) {}
## Error in if (NA) { : missing value where TRUE/FALSE needed
This can happen accidentally as the results of calculations:
if(TRUE && sqrt(-1)) ...
Does java.util.List.isEmpty() check if the list itself is null? [duplicate]
Does java.util.List.isEmpty() check if the list itself is null , or do I have to do this check myself?
8 Answers
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Check if a path represents a file or a folder
I need a valid method to check if a String represents a path for file or a directory. What are valid directory names in Android? As it comes out, folder names can contain '.' chars, so how does system understand whether there's a file or a folder?
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Check if a folder exist in a directory and create them using C#
How can I check if directory C:/ contains a folder named MP_Upload , and if it does not exist, create the folder automatically?
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Create a folder if it doesn't already exist
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Try this, using mkdir:
if (!file_exists('path/to/directory')) {
mkdir('path/to/directory', 0777, true);
}
Note that 0777 is already the default mode for directories and may still be modified by the current umask.
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If isset $_POST
I have a form on one page that submits to another page. There, it checks if the input mail is filled. If so then do something and if it is not filled, do something else. I don't understand why it always says that it is set, even if I send an empty form. What is missing or wrong?
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Assign variable value inside if-statement [duplicate]
...can be assigned but not declared inside the conditional statement:
int v;
if((v = someMethod()) != 0) return true;
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Check if string contains only whitespace
How can I test if a string contains only whitespace?
11 Answers
11
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Check if a user has scrolled to the bottom
...he .scroll() event on window, like this:
$(window).scroll(function() {
if($(window).scrollTop() + $(window).height() == $(document).height()) {
alert("bottom!");
}
});
You can test it here, this takes the top scroll of the window, so how much it's scrolled down, adds the height of th...
How to tell if a tag failed to load
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The "onload" listener will be fired even if there's a javascript error.
– Luca Matteis
Feb 11 '09 at 21:38
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