jasmine 2.1 - CustomMatcher -- toBeNearTo

gistfile1.js

jasmine.addMatchers({
    toBeNearTo: function (utils, customEqualityTesters) {
        return {
            compare: function(actual, expected, within) {
                var diff,
                    result = {};
                within = Math.abs(within) || 1;
                diff = Math.abs(actual - expected);
    
                result.pass = diff <= within;
    
                if (result.pass) {
                    result.message = "Expected " + actual + " to be within " + within + " of " + expected + ".";
                } else {
                    result.message = "Expected " + actual + " to be within " + within + " of " + expected + ", but was within " + diff + ".";
                }
    
                return result;
            }
        }
    }
});