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Comma Operator (,)

Causes two expressions to be executed sequentially.

expression1, expression2


Any expression.


Any expression.

The , operator causes the expressions on either side of it to be executed in left-to-right order, and obtains the value of the expression on the right. The most common use for the , operator is in the increment expression of a for loop. For example:

var i, j, k;
for (i = 0; i < 10; i++, j++) {
   k = i + j;

The for statement only allows a single expression to be executed at the end of every pass through a loop. The , operator is used to allow multiple expressions to be treated as a single expression, thereby getting around the restriction.