What will the output be when using eval on the valueOf method of a String object containing '2 + 2'?

When using eval on the value of the valueOf method from a String object containing '2 + 2', the output will be 4.

The valueOf method of a String object returns the primitive value of the specified object, which in this case would be the string '2 + 2'. When the eval function is called with this string, it evaluates the expression contained within the string. Since '2 + 2' is a valid JavaScript expression, eval processes it and computes the result, which is the numeric value 4.

In this way, eval executes the string as if it were actual JavaScript code, allowing it to perform the addition operation inherent in the expression. Thus, the output is the numerical result of the operation, which is 4.