#explain-js-type-coercion-in-js: convert to boolean

spec.js

describe("toBoolean", function() {
    
    var toBool = toBoolean;
    
    it("should return true for all objects", function() {
        expect(toBool({})).toBe(true);
        expect(toBool([])).toBe(true);
    });
    
    it("should return false for falsy values", function() {
        expect(toBool(0)).toBe(false);
        expect(toBool(NaN)).toBe(false);
        expect(toBool(false)).toBe(false);
        expect(toBool(null)).toBe(false);
        expect(toBool(undefined)).toBe(false);
        expect(toBool('')).toBe(false);
    });
    
    it("should return true for truthy values", function() {
        expect(toBool(1)).toBe(true);
        expect(toBool(true)).toBe(true);
        expect(toBool(new Object())).toBe(true);
        expect(toBool('a')).toBe(true);
    });
});

to_boolean.js

function toBoolean(value) {
    if (typeof value == 'object' && value !== null) return true;
    // NaN !== NaN
    if (typeof value == 'number' && isNaN(value)) return false;
    switch(value) {
        // strict match
        case 0:
        case false:
        case '':
        case null:
        case undefined:
            return false;
        default:
            return true;
    }
}