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Omar Dulaimi
Omar Dulaimi

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How to deprecate functions in Nodejs?

Did you know that the ๐—ก๐—ผ๐—ฑ๐—ฒ๐—ท๐˜€ ๐˜‚๐˜๐—ถ๐—น module lets you deprecate functions and classes?

The ๐˜‚๐˜๐—ถ๐—น.๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ฒ method wraps your function/class in a way that makes it deprecated. When your function/class gets called, a ๐——๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป๐—ช๐—ฎ๐—ฟ๐—ป๐—ถ๐—ป๐—ด will be emitted using the ๐˜„๐—ฎ๐—ฟ๐—ป๐—ถ๐—ป๐—ด event. The emitted event will be outputted to ๐˜€๐˜๐—ฑ๐—ฒ๐—ฟ๐—ฟ 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 --๐—ป๐—ผ-๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป or --๐—ป๐—ผ-๐˜„๐—ฎ๐—ฟ๐—ป๐—ถ๐—ป๐—ด๐˜€ command-line flags are used, or if the ๐—ฝ๐—ฟ๐—ผ๐—ฐ๐—ฒ๐˜€๐˜€.๐—ป๐—ผ๐——๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป property is set to true prior to the first deprecation warning, the ๐˜‚๐˜๐—ถ๐—น.๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ฒ method does nothing.

If the --๐˜๐—ฟ๐—ฎ๐—ฐ๐—ฒ-๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป or --๐˜๐—ฟ๐—ฎ๐—ฐ๐—ฒ-๐˜„๐—ฎ๐—ฟ๐—ป๐—ถ๐—ป๐—ด๐˜€ command-line flags are set, or the ๐—ฝ๐—ฟ๐—ผ๐—ฐ๐—ฒ๐˜€๐˜€.๐˜๐—ฟ๐—ฎ๐—ฐ๐—ฒ๐——๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป property is set to true, a warning and a stack trace are printed to ๐˜€๐˜๐—ฑ๐—ฒ๐—ฟ๐—ฟ the first time the deprecated function is called.

If the --๐˜๐—ต๐—ฟ๐—ผ๐˜„-๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป command-line flag is set, or the ๐—ฝ๐—ฟ๐—ผ๐—ฐ๐—ฒ๐˜€๐˜€.๐˜๐—ต๐—ฟ๐—ผ๐˜„๐——๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป property is set to true, then an exception will be thrown when the deprecated function is called.

The --๐˜๐—ต๐—ฟ๐—ผ๐˜„-๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป command-line flag and ๐—ฝ๐—ฟ๐—ผ๐—ฐ๐—ฒ๐˜€๐˜€.๐˜๐—ต๐—ฟ๐—ผ๐˜„๐——๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป property take precedence over --๐˜๐—ฟ๐—ฎ๐—ฐ๐—ฒ-๐—ฑ๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป and ๐—ฝ๐—ฟ๐—ผ๐—ฐ๐—ฒ๐˜€๐˜€.๐˜๐—ฟ๐—ฎ๐—ฐ๐—ฒ๐——๐—ฒ๐—ฝ๐—ฟ๐—ฒ๐—ฐ๐—ฎ๐˜๐—ถ๐—ผ๐—ป.

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

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deprecate functions in nodejs

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