sniff

JS Type and Prototype Sniffing

npm install sniff
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sniff

This is a simple wrapper to Angus Croll's typeOf function defined in his article Fixing the Javascript typeof operator.

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Why Sniff?

Packaged as a module, sniff is ultraconvenient.

Additionally, it includes a subsequent test to determine whether a function is a functional prototype, and therefore something that would be suitable for calling with the new operator. A value of prototype is returned from the function in event that:

  • the target has been detected as a function through Angus's previous logic

  • the prototype of the function has some keys defined on it. While this is not a conclusive test (suggestions definitely welcome) I think it covers most of the cases where people are using JS prototypes in their code.

Detecting Function Signature Helper

A small helper has been added to sniff to assist with the process of determining the function signature that a function has been called with. This code was written to help with those cases where you have a function that might be called with a variety of different combinations and permutations.

In simple cases, while you might do something like the following:

function example(name, opts, callback) {
  if (typeof opts == 'function') {
    callback = opts;
    opts = {};
  }

  // rest of your function here
}

This can get tiresome and somewhat error prone when you have more complicated functions. This is where the sniff.args helper can come in handy.

For example, this next function is designed to be called with just a name, or a name and an age, or name, age and callback, etc, etc. While writing a function like this would probably generally be discouraged in JS every now and again they are needed.

Anyway, let's take a look:

var sniff = require('sniff');

function example(name, age, opts, callback) {
  // first analyse the arguments and get a matcher function
  var matchSig = sniff.args(arguments);

  // check for the name, age and callback case
  if (matchSig('string', 'number|string', 'function')) {
    // remap opts
    callback = opts;
    opts = {};
  }
  // or the name, opts, function case
  else if (matchSig('string', 'object', 'function')) {
    // remap age, opts, and the callback
    callback = opts,
    opts = age;
    age = null;
  }
}

NOTE: The sniff.args function helper is deprecated, as I believe this can probably be done a better way, and will have a look at it one day...

License(s)

MIT

Copyright (c) 2013 Damon Oehlman damon.oehlman@gmail.com

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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