How to deprecate functions in Nodejs?

Did you know that the 𝗡𝗼𝗱𝗲𝗷𝘀 𝘂𝘁𝗶𝗹 module lets you deprecate functions and classes?

The 𝘂𝘁𝗶𝗹.𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗲 method wraps your function/class in a way that makes it deprecated. When your function/class gets called, a 𝗗𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻𝗪𝗮𝗿𝗻𝗶𝗻𝗴 will be emitted using the 𝘄𝗮𝗿𝗻𝗶𝗻𝗴 event. The emitted event will be outputted to 𝘀𝘁𝗱𝗲𝗿𝗿 the very first time the function gets called. After that, any later calls won't log the warning.

Related options and flags:

If either the --𝗻𝗼-𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 or --𝗻𝗼-𝘄𝗮𝗿𝗻𝗶𝗻𝗴𝘀 command-line flags are used, or if the 𝗽𝗿𝗼𝗰𝗲𝘀𝘀.𝗻𝗼𝗗𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 property is set to true prior to the first deprecation warning, the 𝘂𝘁𝗶𝗹.𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗲 method does nothing.

If the --𝘁𝗿𝗮𝗰𝗲-𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 or --𝘁𝗿𝗮𝗰𝗲-𝘄𝗮𝗿𝗻𝗶𝗻𝗴𝘀 command-line flags are set, or the 𝗽𝗿𝗼𝗰𝗲𝘀𝘀.𝘁𝗿𝗮𝗰𝗲𝗗𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 property is set to true, a warning and a stack trace are printed to 𝘀𝘁𝗱𝗲𝗿𝗿 the first time the deprecated function is called.

If the --𝘁𝗵𝗿𝗼𝘄-𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 command-line flag is set, or the 𝗽𝗿𝗼𝗰𝗲𝘀𝘀.𝘁𝗵𝗿𝗼𝘄𝗗𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 property is set to true, then an exception will be thrown when the deprecated function is called.

The --𝘁𝗵𝗿𝗼𝘄-𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 command-line flag and 𝗽𝗿𝗼𝗰𝗲𝘀𝘀.𝘁𝗵𝗿𝗼𝘄𝗗𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 property take precedence over --𝘁𝗿𝗮𝗰𝗲-𝗱𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻 and 𝗽𝗿𝗼𝗰𝗲𝘀𝘀.𝘁𝗿𝗮𝗰𝗲𝗗𝗲𝗽𝗿𝗲𝗰𝗮𝘁𝗶𝗼𝗻.

Check the snap below to see how it can be used.

Did you learn something new today?

Like and share this post, and follow me for more!