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You can use the comma operator when you want to include multiple expressions in a location that requires a single expression. The most common usage of this operator is to supply multiple updaters in a for loop. For an id
Using the comma operator to join assignments
Because commas have the lowest precedence — even lower than assignment — commas can be used to join multiple assignment expressions. In the following example, a is set to the value of b = 3 (which is 3). Then, the c = 4
Another example that one could make with the comma operator is processing before returning. As stated, only the last element will be returned but all others are going to be evaluated as well. So, one could do:
Another example that one could make with the comma operator is processing before returning. As stated, only the last element will be returned but all others are going to be evaluated as well. So, one could do:
Another example that one could make with the comma operator is processing before returning. As stated, only the last element will be returned but all others are going to be evaluated as well. So, one could do:
You can enter indirect eval with this technique, because direct eval requires the function call to happen on the reference to the eval() function.
You can enter indirect eval with this technique, because direct eval requires the function call to happen on the reference to the eval() function.
This page was last modified on Jul 8, 2025 by MDN contributors.