Salesforce JavaScript Developer Practice Exam

Given the expression +true; !'Lydia'; what will be the outputs?

1. 1 and false

2. false and NaN

3. false and false

4. true and false

The correct answer is: 1 and false

To evaluate the provided expression, let's break it down step by step. Firstly, the expression uses the unary plus operator (`+`) with the boolean value `true`. The unary plus operator converts the operand to a number. In JavaScript, `true` evaluates to `1` when converted to a number. Therefore, the first part of the expression, `+true`, outputs `1`. Next, the expression includes the negation operator (`!`) applied to the string `'Lydia'`. In JavaScript, when a non-empty string is evaluated in a boolean context, it is considered `truthy`. Applying the negation operator to a truthy value (`'Lydia'`) will give `false`. Thus, `!'Lydia'` outputs `false`. Putting both outputs together, the expression `+true; !'Lydia';` results in the outputs `1` for the first part and `false` for the second. The correct answer aligns with this rationale, as it correctly summarizes the outputs of the expressions evaluated.