Expect

Contract by design explicit type checking.

Scoped package

This is a scoped package. Be sure to use the @joezone prefix for both your package dependency and any require statements.

"dependencies": {
  "@joezone/expect": "^0.9.4"
}
 
require('@joezone/expect') 

expect()

The expect function returns true if the type of the first parameter is equal to the spelled-out type in the second parameter. It logs a message to the console, and returns false, whenever an unexpected type is encountered.

Boolean expect(variable, {String|Array} expectedType, String message)
@param variable is the object to test.
@param expectedType is the string value of the type as returned by the variable.constructor.name property. When an object can legitimately hold two or more types, expectedType should be an array of strings containing each of the possible legitimate types.
@param message (optional) is a string to write with the console message if the variable is not of the expected type.
@return true if the expected type was found, false if not.

Cookbook

// ECMAScript types
var alpha = '';
var num = 1;
var obj = {};
var arr = [];
var date = new Date();
var func = function (){};
var regex = /test/i;
var bool = true;
var nullvar = null;
var undef = undefined;

// User-defined types	
class Complex {};
class MoreComplex extends Complex {}; 
var complex = new Complex();
var moreComplex = new MoreComplex();
var unassigned;

// Usage
expect(alpha, 'String');
expect(num, 'Number');
expect(obj, 'Object');	
expect(arr, 'Array');
expect(date, 'Date');	
expect(func, 'Function');	
expect(regex, 'RegExp');	
expect(bool, 'Boolean');	
expect(nullvar, 'null');	
expect(undef, 'undefined');	
expect(complex, 'Complex');	
expect(moreComplex, 'MoreComplex');	
expect(unassigned, ['undefined','Complex','MoreComplex']);