Generic answer This error is caused when you call a function that expects an Object as its argument, but pass undefined or null instead, like for example As that is usually by mistake, the solution is to check your code and fix the null/undefined condition so that the function either gets a proper Object, or does not get called at all. Answer specific to … Read more
Javascript is very flexible with regards to checking for “null” values. I’m guessing you’re actually looking for empty strings, in which case this simpler code will work: Which will check for empty strings (“”), null, undefined, false and the numbers 0 and NaN Please note that if you are specifically checking for numbers it is a common mistake to miss 0 with this method, … Read more
An “undefined variable” is different from the value undefined. An undefined variable: A variable with the value undefined: When a function takes an argument, that argument is always declared even if its value is undefined, and so there won’t be any error. You are right about != null followed by !== undefined being useless, though.
An “undefined variable” is different from the value undefined. An undefined variable: A variable with the value undefined: When a function takes an argument, that argument is always declared even if its value is undefined, and so there won’t be any error. You are right about != null followed by !== undefined being useless, though.
Let’s evaluate the parsing of each: http://jsfiddle.net/brandonscript/Y2dGv/ The tl;dr here: The fragment in the json2 variable is the way the JSON spec indicates null should be represented. But as always, it depends on what you’re doing — sometimes the “right” way to do it doesn’t always work for your situation. Use your judgement and make an informed decision. JSON1 {} This returns an empty … Read more
Let’s evaluate the parsing of each: http://jsfiddle.net/brandonscript/Y2dGv/ The tl;dr here: The fragment in the json2 variable is the way the JSON spec indicates null should be represented. But as always, it depends on what you’re doing — sometimes the “right” way to do it doesn’t always work for your situation. Use your judgement and make an informed decision. JSON1 {} This returns an empty … Read more
Is null an instance of anything? No, there is no type which null is an instanceof. 15.20.2 Type Comparison Operator instanceof At run time, the result of the instanceof operator is true if the value of the RelationalExpression is not null and the reference could be cast to the ReferenceType without raising a ClassCastException. Otherwise the result is false. This means that for any type E and R, for any E o, where o == null, o … Read more
In C++ NULL expands to 0 or 0L. See this quote from Stroustrup’s FAQ: Should I use NULL or 0? In C++, the definition of NULL is 0, so there is only an aesthetic difference. I prefer to avoid macros, so I use 0. Another problem with NULL is that people sometimes mistakenly believe that … Read more
Most of the times this is a bug in the VM. But it can be caused by any native code (e.g. JNI calls). The hs_err_pidXXX.log file should contain some information about where the problem happened. You can also check the “Heap” section inside the file. Many of the VM bugs are caused by the garbage … Read more
What is the cause? Bottom Line You are trying to use something that is null (or Nothing in VB.NET). This means you either set it to null, or you never set it to anything at all. Like anything else, null gets passed around. If it is null in method “A”, it could be that method “B” passed a null to method “A”. null can have different meanings: Object variables … Read more