Type Wrangler is a very small module that smoothes over some of the gotchas in JavaScript type checking and casting. It behaves the way you (or perhaps just I) would expect type checking to work -- e.g., is.object() only works on objects that are neither
npm install type-wrangleris.object() only works on objects that are neither arrays nor regular expressions. It also makes indexOf() easier to use, and provides search functions. Works in Node; should work in browser as well, exporting the objects is and to into the global namespace.None of these techniques are earth-shattering; most people will use these in their daily work. I just didn't want to have to remember all of them while I was banging out code.
Test coverage is as thorough as my imagination allows. I used Jasmine for unit testing.
All checking is strict, unless otherwise noted. Each function returns either true or false.
* is.undefined( value )
* is.null( value )
* is.empty( value ) - checks for null or undefined
* is.empty.array( value ) or is.emptyArray( value ) - must be an array-like object and have no items
* is.empty.arguments( value ) or is.emptyArguments( value ) - identical to above
* is.empty.object( value ) or is.emptyObject( value ) - must be an object and have no properties of its own; objects with properties in their prototype chains will also fail
* is.null( value )
* is.boolean( value )
* is.nan( value ) - really not necessary, since it merely calls isNan(). But I just included it to be thorough.
* is.infinite( value ) - opposite of isFinite(). I didn't include an isFinite() function because is.number() performs this check.
* is.number( value ) - includes all the sensible numbers (e.g., not NaN or Infinity).
* is.integer( value ) - we all know JavaScript doesn't have integers or floats, so this fills half that gap.
* is.float( value ) - and this fills the other half of the gap.
* is.string( value )
* is.object( value ) - anything considered to be an object, except null, regular expressions, arrays, or array-like objects. Functions are considered objects, of course.
* is.array( value ) - any good old honest 'true' array.
* is.enumerable( value ) - arrays, array-like objects, and strings. Anything that can be iterated upon. (Yes, that does include strings!)
* is.arrayLike( value ) - array-like objects (but not arrays).
* is.arguments( value ) - the arguments array-like object.
* is.function( value )
* is.regexp( value )
* is.in( needle [, haystack] ) - takes a needle and performs a strict search on the haystack. If the haystack is not supplied, this is assumed as the haystack. The haystack can be an object, array-like object, or string. In case of objects, only the self-owned, direct descendants are searched.
* is.in.array( needle [, haystack] ) or is.inArray( needle [, haystack] ) - works on array-like objects only.
* is.in.object( needle [, haystack] ) or is.inObject( needle [, haystack] ) - works only on haystacks that pass the is.object() test.
* is.in.string( needle [, haystack] ) or is.inString( needle [, haystack] ) - string search; converts non-strings to strings.
* is.ownProperty( property [, object] ) - calls Object.prototype.hasOwnProperty() on the object. If the object is not supplied, this is assumed.
* to.boolean( value )
* to.number( value ) or to.float( value ) - calls parseFloat() on the value; therefore, it may return NaN.
* to.integer( value ) - returns the integral part of the value. Acts as floor for positive numbers and ceiling for negative integers.
* to.string( value )
* to.array( value ) - casts array-like objects to arrays and everything else to an array containing a single element, which happens to be the passed value.
* to.regexp( value ) - if the value is a string, returns a regular expression using the new RegExp() constructor. Returns undefined if the value is not a string.
* to.date( value ) - returns a new date object using the new Date() constructor.
More typecasting to follow, as I think of cases that need it!
isNote: This is not the same as the is by Enrico Marino, which is another interesting JavaScript type checking library. He uses some neat techniques, and also adds functions for comparison (e.g., is.gt(), is.odd(), is.divisibleBy()) which I had no interest in. You can find his library at https://github.com/onirame/is
This used to be called Wrangler, but I've changed it to Type Wrangler to accommodate CloudFlare, who have a package of the same name. Apparently it's used for working on their distributed workers, which sound very cool.