"readme":"# once\n\nOnly call a function once.\n\n## usage\n\n```javascript\nvar once = require('once')\n\nfunction load (file, cb) {\n cb = once(cb)\n loader.load('file')\n loader.once('load', cb)\n loader.once('error', cb)\n}\n```\n\nOr add to the Function.prototype in a responsible way:\n\n```javascript\n// only has to be done once\nrequire('once').proto()\n\nfunction load (file, cb) {\n cb = cb.once()\n loader.load('file')\n loader.once('load', cb)\n loader.once('error', cb)\n}\n```\n\nIronically, the prototype feature makes this module twice as\ncomplicated as necessary.\n\nTo check whether you function has been called, use `fn.called`. Once the\nfunction is called for the first time the return value of the original\nfunction is saved in `fn.value` and subsequent calls will continue to\nreturn this value.\n\n```javascript\nvar once = require('once')\n\nfunction load (cb) {\n cb = once(cb)\n var stream = createStream()\n stream.once('data', cb)\n stream.once('end', function () {\n if (!cb.called) cb(new Error('not found'))\n })\n}\n```\n\n## `once.strict(func)`\n\nThrow an error if the function is called twice.\n\nSome functions are expected to be called only once. Using `once` for them would\npotentially hide logical errors.\n\nIn the example below, the `greet` function has to call the callback only once:\n\n```javascript\nfunction greet (name, cb) {\n // return is missing from the if statement\n // when no name is passed, the callback is called twice\n if (!name) cb('Hello anonymous')\n cb('Hello ' + name)\n}\n\nfunction log (msg) {\n console.log(msg)\n}\n\n// this will print 'Hello anonymous' but the logical error will be missed\ngreet(null, once(msg))\n\n// once.strict will print 'Hello anonymous' and throw an error when the callback will be called the second time\ngreet(null, once.strict(msg))\n```\n",
