Print a warning exactly once during development. Suitable for deprecation warnings, warnings for missing setup etc.
Open a Terminal in the project root and run:
npm install warn-once
The warnOnce
function accepts a condition as the first argument. If the condition is true
, then it'll print a warning:
const warnOnce = require('warn-once');
// ...
warnOnce(someCondition, 'This is a warning message');
// additional message strings as parameters
// You can add 'n' number of arguments.
warnOnce(someCondition, 'message 1', 'message 2', 'message 3')
You can call warnOnce
multiple times, but if the warning was printed already, it'll not be printed again.
The warning is only shown during development, i.e. if NODE_ENV
is not set to 'production'
.