Love you, Mom!

I’m constantly confusing myself when calculating timezones for meetings.

9 o’clock a.m. in San Francisco is what time in Madrid? What time is a 3 p.m. meeting in New York? In general, what time is it in Minneapolis?

I’m finally getting around to writing a really simple JS widget to help me calculate differences in key timezones.

However, when calculating the number 0, I was seeing my tests fail and it was a bit confusing.

Turns out the number 0 causes a bit of a hiccup when using short-circuit evaluations.

var zero = 0;

var myVar = zero || 0; // => NaN.

Hmm, confusing.

Some assertions that prove this point:

    TestCase('TestForZero', {
        'test zero' : function() {

            // Set `zero` and `one` to number values:

            var zero = 0;

            assertNotNaN(zero);
            assertNotNull(zero);
            assertNotUndefined(zero);
            assertNumber(zero);

            var one = 1;

            assertNotNaN(one);
            assertNotNull(one);
            assertNotUndefined(one);
            assertNumber(one);

            // If either variable is null, set a string just for fun.
            // Note: Expectation is that *neither* will be null:

            zero = zero || 'zero';
            one = one || 'one';

            // `one` maintains itself.
            // Assertions copied from above:

            assertNotNaN(one);
            assertNotNull(one);
            assertNotUndefined(one);
            assertNumber(one);

            // `zero` unfortunately does not:

            assertNotNull(zero);
            assertNotUndefined(zero);
            assertNaN(zero); // => Gotcha!!
            assertTypeOf('string', zero);

            // Using a more strict ternery operator yields expected results:
            zero = 0;
            zero = (zero !== null) ? zero : 'zero';

            // Assertions copied from above:
            assertNotNaN(zero);
            assertNotNull(zero);
            assertNotUndefined(zero);
            assertNumber(zero);

        }   
    })