Why is there a Plus Symbol Before the Variable `d` in This Code Snippet?

The Purpose of a Plus Symbol Before a Variable

In programming, the symbol can be used in a variety of ways. One common use is to add two numbers together. However, in the context of the code snippet provided:

function addMonths(d, n, keepTime) { 
    if (+d) {

the operator is being used before a variable, d. This syntax might seem puzzling at first, but it serves a specific purpose.

Explanation

The operator in this context is known as the unary plus operator. Its purpose is to coerce an object to a numeric value. By placing the operator before d, the code is implicitly converting d to a number. The result of this operation is then evaluated as a boolean value: if the resulting number is non-zero, the if statement evaluates to true; otherwise, it evaluates to false.

In the code snippet above, this behavior is used to check whether d is a non-zero number. If d is non-zero, the if statement executes its body. If d is zero, the if statement is skipped.

Reference

For more information on the unary plus operator, please refer to the following resources:

• [MDN Web Docs: Unary Operators](https://developer.mozilla.org/en-US/docs/Glossary/Unary_operator)
• [W3Schools: JavaScript Unary Operators](https://www.w3schools.com/js/js_operators_unary.asp)

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