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Immediately invoked function expressions may be written in a number of different ways. [3] A common convention is to enclose the function expression – and optionally its invocation operator – with the grouping operator, [4] in parentheses, to tell the parser explicitly to expect an expression.
C# 6.0 and above have ?., the null-conditional member access operator (which is also called the Elvis operator by Microsoft and is not to be confused with the general usage of the term Elvis operator, whose equivalent in C# is ??, the null coalescing operator) and ?[], the null-conditional element access operator, which performs a null-safe call of an indexer get accessor.
The null coalescing operator is a binary operator that is part of the syntax for a basic conditional expression in several programming languages, such as (in alphabetical order): C# [1] since version 2.0, [2] Dart [3] since version 1.12.0, [4] PHP since version 7.0.0, [5] Perl since version 5.10 as logical defined-or, [6] PowerShell since 7.0.0, [7] and Swift [8] as nil-coalescing operator.
In JavaScript, there are 7 primitive data types: string, number, bigint, boolean, symbol, undefined, and null. [19] Their values are considered immutable. These are not objects and have no methods or properties; however, all primitives except undefined and null have object wrappers. [20]
Thus (x === undefined) is not a foolproof way to check whether a variable is undefined, because in versions before ECMAScript 5, it is legal for someone to write var undefined = "I'm defined now";. A more robust approach is to compare using (typeof x === 'undefined'). Functions like this won't work as expected:
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A function which never returns has an undefined value because the value can never be observed. Such functions are formally assigned the bottom type, which has no values. Examples fall into two categories: Functions which loop forever. This may arise deliberately, or as a result of a search for something which will never be found.
World No. 2-ranked Alexander Zverev withdrew from the United Cup mixed teams tennis tournament on Wednesday with a biceps strain less than two weeks from the start of the Australian Open.