Salesforce JavaScript Developer Practice Exam

What does the eval function return when a String object is evaluated?

1. 4

2. "2 + 2"

3. NaN

4. Syntax error

The correct answer is: "2 + 2"

The eval function, when applied to a String object, evaluates the string as JavaScript code. If the string is a valid expression, it will return the result of that expression. In this case, when the string "2 + 2" is evaluated, it interprets it as a mathematical expression and computes the value. Therefore, the output will be the result of the addition operation, which is 4. However, if the string were just passed as it is, without evaluation (e.g., without being executed within the eval function), it would merely be returning the original string representation of the input. This scenario clarifies that string literals do not inherently compute to numerical results; they represent text. When dealing with the other options: - The return of 4 is indeed the result when "2 + 2" is evaluated, but if the eval function is merely inspecting the string itself without evaluating it mathematically, it does not yield that interpretation automatically. - NaN is a return value that represents an invalid number in JavaScript. It would be produced if a string contained a non-numeric calculation that the JavaScript engine couldn’t parse correctly. - A syntax error occurs when the code cannot be parsed, which is only the case