expression1

Any expression.

expression2

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:

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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.

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Concepts