JavaScript - Types, Equality, Conversion and All That Jazz: Serious types(truthy value, falsey value)

Head First JavaScript Programming
( O'Reilly Media)
Eric T. Freeman (著), Elisabeth Robson (著)

開発環境

• OS X Mavericks - Apple(OS)
• Safari, Firefox + Firebug, Google Chrome(Webプラウザ、プラグイン)
• BBEdit - Bare Bones Software, Inc. (GUI) , Emacs (CUI) (Text Editor)
• JavaScript (プログラミング言語)

Head First JavaScript Programming (Eric T. Freeman (著)、 Elisabeth Robson (著)、 O'Reilly Media )のChapter 7(Types, Equality, Conversion and All That Jazz: Serious types)、SHARPEN YOUR PENCIL(p.293)を解いてみる。

SHARPEN YOUR PENCIL(p.293)

コード(BBEdit, Emacs)

var lieDetectorTest = function () {
        var lies = 0,
            stolenDiamond = {},
            car = {
                keysInPocket: null
            },
            foundYouAtTheCrimeScene = [],
            yourName = ' ',
            output = '';
        
        // true
        if (stolenDiamond) {
            print('You stole the diamond');
            lies += 1;
        }
        // false
        if (car.keysInPocket) {
            print('Uh oh, guess you stole the car!');
            lies += 1;
        }
        // false
        if (car.emptyGasTank) {
            print('You drove the car after you stole it!');
            lies += 1;
        }
        // true
        if (foundYouAtTheCrimeScene) {
            print('A sure sign of guilt');
            lies += 1;
        }
        // false
        if (foundYouAtTheCrimeScene[0]) {
            print('Caught with a stolen item!');
            lies += 1;
        }
        // true
        if (yourName) {
            print('Guess you lied about your name');
            lies += 1;
        }
        return lies;
    },
    numberOfLies;

numberOfLies = lieDetectorTest();
print('You told ' + numberOfLies + ' lies!'); // 3

// true
if (numberOfLies >= 3) {
    print('Guilty as charged');
}