The comma operator (,) allows multiple expressions or statements to be written as one statement. Despite its existence, use cases for this operator may be elusive.
Useful Applications
One potential use of the comma operator lies in code minification. For instance, the code below:
if (x) { foo(); return bar(); } else { return 1; }
Can be compressed using the comma operator:
return x ? (foo(), bar()) : 1;
The ternary operator (?) can be used in this case, as the comma operator permits two statements to be written as one. This can result in significant code compression, as seen in this example where the size is reduced from 39 to 24 bytes.
Distinction from Variable Comma
It's crucial to note that the comma in var a, b is distinct from the comma operator. This comma appears in variable declaration statements and has a specific function not related to the comma operator.
In expressions, a, b refers to the variables and evaluates to b, whereas in variable declaration statements, a, b declares both variables.
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