overload-js
v1.0.0
Published
Method overloading in JavaScript
Downloads
2,673
Readme
overload-js
Function overloading in JavaScript for 3.9KB minified, 1.4KB gzipped.
Provides tools to mimic function overloading that is present in most strictly-types languages. Prevents messy, long, if-statement, type-checking functions that are hard to read and maintain. Style and API inspired by Moreiki and Mongoose.
npm install overload-js
Basic Usage
var hello = (function() {
var secret = '!';
return overload()
.args().use(function() {
return secret;
})
.args(String).use(function(val) {
secret = val;
});
}());
hello('world'); // calls setter
hello(); // returns 'world'
hello(0); // throws a Type Error
Detectable types
null
undefined
Infinity
Date
NaN
Number
String
Object
Array
RegExp
Boolean
Function
Element // browser only
Overload with a map
A map can be defined as an overload as well:
var hello = overload.map({
what: String
}).use(function(obj) {
return 'hello ' + obj.what;
});
hello({ what: 'world!' }); // returns 'hello world!'
hello('world'); // throws a Type Error
or a map can be used as a custom type (see below):
var hello = overload.args(String, o.map({
what: String
})).use(function(str, obj) {
return str + obj.what;
});
hello('hello', { what: 'world!' }); // returns 'hello world!'
hello('hello', 'world'); // throws a Type Error
Custom types
A custom type can be defined by passing a string
and validation function
to
defineType
. The validation function will be passed the value to validate
and expects a boolean
return.
overload.defineType('$', function(val) {
return val instanceof jQuery;
});
Custom types are available under o
.
var overload = require('overload-js'),
o = overload.o;
var method = overload().args(o.$).use(function($elem) {
console.log($elem);
});
method(); // fails
method(''); // fails
method($('body')); // succeeds
Additional types
o.any()
accepts multiple types that a parameter will match against.
var method = overload().args(o.any(String, Number)).use(function() {
console.log('passed!');
});
method(); // fails
method([]); // fails
method(''); // passed!
method(0); // passed!
The inverse of o.any
is o.except
.
var method = overload().args(o.except(Object)).use(function() {
console.log('passed!');
});
method(); // passed!
method([]); // passed!
method({}); // fails
Also available are o.truthy
and o.falsy
.
var method = overload()
.args(o.truthy).use(function() {
console.log('truthy');
})
.args(o.falsy).use(function() {
console.log('falsy');
});
method(); // fails
method(0); // falsy
method(1); // truthy
Overloading by length
In addition to overloading by type, argument length can be used.
If a number is not passed, the function.length
will be used.
var method = overload()
.len(0).use(function() {
console.log('0 args');
})
.len(1).use(function(a) {
console.log('1 arg');
})
.len().use(function(a, b, c) {
console.log('3 args');
});
method(); // '0 args'
method({}); // '1 arg'
method(null, [], {}); // '3 args'
alias: count
, size
If args
and length
are used in the overload, args will be matched
first, followed by length.
Fallback
A fallback function can be defined via the fallback
method.
var method = overload().args(String).use(function(a) {
console.log(a);
})
.fallback(function() {
console.log('handled!');
});
method('hello'); // 'hello'
method(); // 'handled'
If a fallback is not defined and the exposed method is called without a matching function, an error will be thrown...
Expose
A clean function can be exposed so that overload properties and methods are hidden from the outside world.
var method = overload()
.args().use(function() {
return 'hi';
})
.expose();
// method.args === undefined
// method.use === undefined
// etc...
Errors
The error from unmatched calls can be handled by defining your own err
method on overload
or
by passing a function to handle the error.
overload.err = function() {
console.log('there was an error');
};
overload()
.error(function() { console.trace(); })
Support
Node.js, modern browsers and IE8+
To run the tests, simply open test/index.html in your favorite browser or run npm test
.
#License
The MIT License (MIT)
Copyright (c) 2014 Joseph Clay
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.