Case-Expression

A case-expression is a control-construct similar to Haskell's case expression.

Synopsis

A case-expression is a bit more powerful than regular switch statements because it allows you to match your expression to arbitrary objects, including functions and regular expressions. The signature for a case-expression is as follows:

caseExpression( <Expression>, [
  <Pattern1>, <Block1>,
  <Pattern2>, <Block2>,
  ...
  <PatternN>, <BlockN>
]);

It takes 2 arguments, an expression used to match against patterns and an associative array of pattern-block pairs. Once a pattern matches, the block following that pattern is evaluated and it's value is returned as the result of the case-expression.

Expressions

Expressions are regular JavaScript values -- Numbers, Strings, Booleans, Objects, etc. These are passed in as the first value of the case-expression and used to match against the patterns in the associative array.

Patterns

Pattern values are very flexible, they can be either predicate functions, regular expressions, or regular JavaScript values.

• Predicates are functions that take the expression as an argument and return a boolean value. If the predicate returns true, the result of the case-expression is the block following the predicate.

• Regular expressions are tested against the given expression and if there is a match, the result of the case-expression is the subsequent block.

• Regular values are tested against the expression via the equality operators.

Blocks

If a block is a function, the function is evaluated and it's result is returned as the value of the case-expression. Otherwise, if the block is another type of value, then that value is returned as the value of the case-expression.

Install

$ npm install case-expression 

Usage

var readline = require( 'readline' );
var _case = require( 'case-expression' );
 
var rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});
 
rl.question( "Do you like node.js? [yes/no]\n", function( ans ) {
  _case( ans, [
    /yes|no/i, function() {
      console.log( 'Thanks for your feedback!' );
      rl.close();
    },
    /.*/, function() {
      console.log( 'Ok...I see you have a penchant for following simple directions!' );
      rl.close();
    }
  ]);
});

License

The MIT License (MIT)

Copyright © 2015 Seth Bonnie

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.