A question about union in C – store as one type and read as another – is it implementation defined?

This is undefined behaviour. u.i and u.ch are located at the same memory address. So, the result of writing into one and reading from the other depends on the compiler, platform, architecture, and sometimes even compiler’s optimization level. Therefore the output for u.i may not always be 515. Example For example gcc on my machine …

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How to assign string | undefined to string in TypeScript?

The typescript compiler performs strict null checks, which means you can’t pass a string | undefined variable into a method that expects a string. To fix this you have to perform an explicit check for undefined before calling luminaireReplaceLuminaire(). In your example: private selectedSerialForReplace(): string | undefined { return this.selectedSerials.pop(); } luminaireReplaceLuminaire(params: { “serial”: string; …

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undefined == undefined is true. But undefined >= undefined is false?

The >= operator is essentially the negation of the < operator. And both invoke the Abstract Relational Comparison Algorithm which returns undefined for undefined >= undefined as defined in step 3 (a to c). Actually, you can also see that the greater-than(-or-equal) and less-than(-or-equal) operators are only meant to work with either numbers or strings. …

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JavaScript “cannot read property “bar” of undefined [duplicate]

If an object’s property may refer to some other object then you can test that for undefined before trying to use its properties: if (thing && thing.foo) alert(thing.foo.bar); I could update my answer to better reflect your situation if you show some actual code, but possibly something like this: function someFunc(parameterName) { if (parameterName && …

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When do I initialize variables in JavaScript with null or not at all?

The first example doesn’t assign anything to the variable, so it implicitly refers to the undefined value (see 10.5 in the spec for the details). It is commonly used when declaring variables for later use. There is no need to explicitly assign anything to them before necessary. The second example is explicitly assigned null (which …

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