16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
61 lines
1.6 KiB
Plaintext
61 lines
1.6 KiB
Plaintext
== Why is this an issue?
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Functions that accept random numbers of arguments use a rest argument (``++... argname++``). This allows you to pass the function each relevant parameter individually. At runtime, those parameters are automatically wrapped in an array. If you pass an array to such a function, it will automatically be re-wrapped in another array, and this double-layering won't be expected by the called function. To avoid that double-layering, use the spread operator (``++...++``arrayToBeExpanded) in the call to expand the array.
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This applies both to manually created arrays, and to arguments that were accepted as rest parameters.
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=== Noncompliant code example
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[source,javascript]
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----
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collect(new Book(), new Book());
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function collect(...books: Book[]) {
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buy(books); // Noncompliant
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}
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function buy(...things: any[]) {
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console.log(things); // outputs "[ [ Book {}, Book {} ] ]"
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}
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----
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=== Compliant solution
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[source,javascript]
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----
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collect(new Book(), new Book());
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function collect(...books: Book[]) {
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buy(...books);
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}
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function buy(...things: any[]) {
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console.log(things); // outputs "[ Book {}, Book {} ]"
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}
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----
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Use spread operator '...' to pass this argument
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'''
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== Comments And Links
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(visible only on this page)
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=== on 3 Jan 2018, 20:37:24 Ann Campbell wrote:
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\[~elena.vilchik] a little text on what "spread" is and why it's necessary (when the argument you're passing is apparently already an array) would be nice.
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endif::env-github,rspecator-view[]
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