Tests for .valueAsNumber with . On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". PASS valueAsNumberFor("") is Number.NaN PASS valueAsNumberFor("1969-12-31") is Date.UTC(1969, 11, 31) PASS valueAsNumberFor("1970-01-01") is Date.UTC(1970, 0, 1) PASS valueAsNumberFor("2009-12-22") is Date.UTC(2009, 11, 22) PASS setValueAsNumberAndGetValue(1969, 11, 1) is "1969-12-01" PASS setValueAsNumberAndGetValue(1970, 0, 1) is "1970-01-01" PASS setValueAsNumberAndGetValue(2009, 11, 31) is "2009-12-31" PASS setValueAsNumberAndGetValue(10000, 0, 1) is "10000-01-01" PASS setValueAsNumberAndGetValue(-1, 0, 1) is "" PASS setValueAsNumberAndGetValue(0, 11, 31) is "" PASS setValueAsNumberAndGetValue(1, 0, 1) is "0001-01-01" PASS setValueAsNumberAndGetValue(275760, 8, 13) is "275760-09-13" Tests to set invalid values to valueAsNumber: PASS input.value = ""; input.valueAsNumber = null; input.value is "1970-01-01" PASS input.valueAsNumber = "foo"; input.valueAsNumber is NaN PASS input.valueAsNumber = "foo"; input.value is "" PASS input.valueAsNumber = NaN; input.valueAsNumber is NaN PASS input.valueAsNumber = NaN; input.value is "" PASS input.valueAsNumber = Number.NaN; input.valueAsNumber is NaN PASS input.valueAsNumber = Number.NaN; input.value is "" PASS input.valueAsNumber = Infinity threw exception TypeError: Failed to set the 'valueAsNumber' property on 'HTMLInputElement': The value provided is infinite.. PASS input.valueAsNumber = Number.POSITIVE_INFINITY threw exception TypeError: Failed to set the 'valueAsNumber' property on 'HTMLInputElement': The value provided is infinite.. PASS input.valueAsNumber = Number.NEGATIVE_INFINITY threw exception TypeError: Failed to set the 'valueAsNumber' property on 'HTMLInputElement': The value provided is infinite.. PASS input.valueAsNumber = Date.UTC(275760, 8, 14); input.valueAsNumber is NaN PASS input.valueAsNumber = Date.UTC(275760, 8, 14); input.value is "" PASS successfullyParsed is true TEST COMPLETE