JavaScript syntax
part 5/59 · 107.4 KB total
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The five problematic tokens are the open parenthesis "(", open bracket "[", slash "/", plus "+", and minus "-". Of these, the open parenthesis is common in the immediately invoked function expression pattern, and open bracket occurs sometimes, while others are quite rare. An example:
a = b + c
(d + e).foo()
// Treated as:
// a = b + c(d + e).foo();
with the suggestion that the preceding statement be terminated with a semicolon.
Some suggest instead the use of leading semicolons on lines starting with '(' or '[', so the line is not accidentally joined with the previous one. This is known as a defensive semicolon, and is particularly recommended, because code may otherwise become ambiguous when it is rearranged. For example:
a = b + c
;(d + e).foo()
// Treated as:
// a = b + c;
// (d + e).foo();
Initial semicolons are also sometimes used at the start of JavaScript libraries, in case they are appended to another library that omits a trailing semicolon, as this can result in ambiguity of the initial statement.
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