Simple example

// This line is for NodeJS. In browser, you just have to the JS-File
// using <script src="..." type="text/javascript"></script>
var VC = require('valuechecker');

/**
 * This method demonstrates the ValueChecker interface.
 *
 * @param {String} a_string  A string with length between 10 and 12.
 * @param {Integer} an_int   Just an int.
 * @param {CoolObj} cool_obj An object of type CoolObj.
 */
function noop(a_string, an_int, cool_obj) {
    a_string = VC.string(a_string, "a_string", null, 12, 10);
    an_int = VC.int(an_int, "an_int");
    cool_obj = VC.instance_of(cool_obj, "cool_obj", CoolObj);
};

The ValueChecker methods checks the given value for the type and additional criteria you want to check. If it does not match, an exception is thrown telling exactly what has happend (e.g. type mismatch or string is too short etc). If it does match, the value to check is returned casted to the type you wanted. Therefore if you pass for instance the string "2" to VC.int, then it will pass the test an the int value 2 will be returend. Because "2" is lossless convertable to an int.