wtf

Tiny JS type-checking library.

Install

node.js

npm install wtf-is

var wtf = require('wtf-is');

browser

git clone this repo, or download wtf.js or wtf.min.js

Include the script as an AMD module, or directly in a script tag.

require(['wtf'], function(wtf) {
  // use the library
});

<script src="path/to/wtf.min.js"></script>

Using the script tag creates a global variable wtf

Usage

Basic type-checking: wtf.is(<thing>)

wtf.is('this');   // 'string'
wtf.is(3.14);     // 'float'
wtf.is([0,1,2]);  // 'array'
wtf.is(wtf);      // 'function'
wtf.is(Infinity); // 'infinite'
wtf.is(0 / 0);    // 'NaN'
wtf.is(1024);     // 'integer'

wtf.is() distinguishes integers from floats.

Before you send me nasty emails, I know JavaScript only has one Number type. This is done simply because it is potentially useful to know when a number is an integer or not, especially when...

Handling input: wtf(<thing>).switch({types})

// assume someThing expects a percentage alpha value
//  but you want users to be able to provide 0-255 as well
function setAlpha(number) {
  wtf(number).switch({
    integer: function() {
      someThing.alpha = number / 255;
    },
    float: function() {
      someThing.alpha = number
    }
  });
}

You can also simply use number: if you want to match both integers and floats.

function unknownInputType(input) {
  wtf(input).switch({
    number: function() {
      // do something with a number
    },
    string: function() {
      // do something else with a string
    },
    undefined: function() {
      // if no input was passed
    },
    default: function() {
      // any type that wasn't specified above
    }
  });
}

Use the internals:

cross-platform versions of the checks built-in to modern browsers

wtf.isNaN(0 / 0);    // true
wtf.isNaN('blabla'); // false
wtf.isArray([]);     // true
wtf.isFinite(Number.MAX_VALUE * 2); // false