What does the !! (double exclamation mark) operator do in JavaScript . . . A third use is to produce logical XOR and logical XNOR In both C and JavaScript, a b performs a logical AND (true if both sides are true), and a b performs a bitwise AND a || b performs a logical OR (true if at least one are true), and a | b performs a bitwise OR
Which equals operator (== vs ===) should be used in JavaScript . . . JavaScript has two sets of equality operators: === and !==, and their evil twins == and != The good ones work the way you would expect The good ones work the way you would expect If the two operands are of the same type and have the same value, then === produces true and !== produces false
Is there a null coalescing operator in JavaScript? After reading your clarification, @Ates Goral's answer provides how to perform the same operation you're doing in C# in JavaScript @Gumbo's answer provides the best way to check for null; however, it's important to note the difference in == versus === in JavaScript especially when it comes to issues of checking for undefined and or null
How do you use the ? : (conditional) operator in JavaScript? It's a little hard to google when all you have are symbols ;) The terms to use are "JavaScript conditional operator" If you see any more funny symbols in JavaScript, you should try looking up JavaScript's operators first: Mozilla Developer Center's list of operators The one exception you're likely to encounter is the $ symbol
JavaScript OR (||) variable assignment explanation - Stack Overflow That is, JavaScript "short-circuits" the evaluation of Boolean operators and will return the value associated with either the first non-false variable value or whatever the last variable contains See Anurag's explanation of those values that will evaluate to false