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How to check for an undefined or null variable in JavaScript?
... property doesn't yield an error and simply returns undefined, which, when converted to a boolean, evaluates to false. So, if you don't care about
0 and false, using if(obj.undefProp) is ok. There's a common idiom based on this fact:
value = obj.prop || defaultValue
which means "if obj has the p...
Primary key/foreign Key naming convention [closed]
...e the USING syntax in SQL to save some typing and some boilerplate noise:
SELECT name, address, amount
FROM employees JOIN payroll USING (employee_id)
Another argument in favor of convention #2 is that it's the way the relational model was designed.
The significance of each column is
part...
Capybara Ambiguity Resolution
...t
So it's adviced to choose another, less ambiguous locator: for example select element by id, class or other css/xpath locator so that only one element will match it.
As a note here are some locators that I usually consider useful when resolving ambiguity:
find('ul > li:first-child')
It'...
AsyncTask and error handling on Android
I'm converting my code from using Handler to AsyncTask . The latter is great at what it does - asynchronous updates and handling of results in the main UI thread. What's unclear to me is how to handle exceptions if something goes haywire in AsyncTask#doInBackground .
...
Excel “External table is not in the expected format.”
...e same problem. which as resolved using these steps:
1.) Click File
2.) Select "save as"
3.) Click on drop down (Save as type)
4.) Select Excel 97-2003 Workbook
5.) Click on Save button
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How to set data attributes in HTML elements
...e.
$("#button").on("click", function() {
var field = document.querySelector("#textfield")
switch ($("#method").val()) {
case "setAttribute":
field.setAttribute("data-customval", field.value)
break;
case "dataset":
field.dataset.customval = field.value
...
How do you produce a .d.ts “typings” definition file from an existing JavaScript library?
...ucco-and-Luke-Hoban-Inside-TypeScript at 00:33:52 they had built a tool to convert WebIDL and WinRT metadata into TypeScript d.ts
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How to check if activity is in foreground or in visible background?
...stem dialogue box pops-up and I only want to finish() ; once the user has selected an option from the dialogue box?
23 An...
How to use a variable for a key in a JavaScript object literal?
... 'theTop' : 10 }
The PropertyName theTop is an IdentifierName, so it gets converted to the 'theTop' string value, which is the string value of 'theTop'.
It is not possible to write object initializers (literals) with variable keys.
The only three options are IdentifierName (expands to string liter...
JavaScript open in a new window, not tab
I have a select box that calls window.open(url) when an item is selected. Firefox will open the page in a new tab by default. However, I would like the page to open in a new window, not a new tab.
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