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I found this in a piece of code and i'm wondering what it does? Assign b to x... but what's with the ,c?
var x = b, c;
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In JavaScript, there's a standard comma style for adding commas to our code. For multiple variable variables and constant declarations, we have a line break after a comma. This also applies if we have long expressions in arrays or having a list of properties inside an object.
In Java, the comma is a separator used to separate elements in a list in various contexts. It is not an operator and does not evaluate to the last element in the list.
The comma operator (,) allows you to evaluate multiple expressions wherever a single expression is allowed. The comma operator evaluates the left operand, then the right operand, and then returns the result of the right operand. First the left operand of the comma operator is evaluated, which increments x from 1 to 2.
The comma operator in c comes with the lowest precedence in the C language. The comma operator is basically a binary operator that initially operates the first available operand, discards the obtained result from it, evaluates the operands present after this, and then returns the result/value accordingly.
That declares two variables, x and c, and assigns value b to variable x.
This is equivalent to the more explicit form*:
var x = b;
var c;
JavaScript allows multiple declarations per var keyword – each new variable is separated by a comma. This is the style suggested by JSLint, which instructs developers to use a single var per function (the error message from JSLint is Combine this with the previous 'var' statement.).
* Actually, due to hoisting it will be interpreted as var x; var c; x = b.
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