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In object-oriented computer programming, a null object is an object with no referenced value or with defined neutral (null) behavior.The null object design pattern, which describes the uses of such objects and their behavior (or lack thereof), was first published as "Void Value" [1] and later in the Pattern Languages of Program Design book series as "Null Object".
In JavaScript, the empty string (""), null, undefined, NaN, +0, −0 and false [28] are sometimes called falsy (of which the complement is truthy) to distinguish between strictly type-checked and coerced Booleans (see also: JavaScript syntax#Type conversion). [29] As opposed to Python, empty containers (Arrays, Maps, Sets) are considered truthy.
This is the template test cases page for the sandbox of Template:If empty Purge this page to update the examples. If there are many examples of a complicated template, later ones may break due to limits in MediaWiki ; see the HTML comment " NewPP limit report " in the rendered page.
A string in JavaScript is a sequence of characters. In JavaScript, strings can be created directly (as literals) by placing the series of characters between double (") or single (') quotes. Such strings must be written on a single line, but may include escaped newline characters (such as \n).
The empty string has several properties: |ε| = 0. Its string length is zero. ε ⋅ s = s ⋅ ε = s. The empty string is the identity element of the concatenation operation. The set of all strings forms a free monoid with respect to ⋅ and ε. ε R = ε. Reversal of the empty string produces the empty string, so the empty string is a palindrome.
In JavaScript, the empty string (""), null, undefined, NaN, +0, −0 and false [3] are sometimes called falsy (of which the complement is truthy) to distinguish between strictly type-checked and coerced Booleans (see also: JavaScript syntax#Type conversion). [4] As opposed to Python, empty containers (Arrays, Maps, Sets) are considered truthy.
The #if function selects one of two alternatives based on the truth value of a test string. {{#if: test string | value if true | value if false}} As explained above, a string is considered true if it contains at least one non-whitespace character. Any string containing only whitespace or no characters at all will be treated as false.
The JavaScript language does not have a built-in NOP statement. Many implementations are possible: Use the ; empty statement [14] or the {} empty block statement the same way as in the C and derivatives examples; Use the undefined or the null expression as a complete statement (an expression statement) when the previous methods are not allowed ...