javascript - 查找对象中键的数量

Question

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How to efficiently count the number of keys/properties of an object in JavaScript?

var values = [{
    'SPO2': 222.00000,
    'VitalGroupID': 1152,
    'Temperature': 36.6666666666667,
    'DateTimeTaken': '/Date(1301494335000-0400)/',
    'UserID': 1,
    'Height': 182.88,
    'UserName': null,
    'BloodPressureDiastolic': 80,
    'Weight': 100909.090909091,
    'TemperatureMethod': 'Oral',
    'Resprate': null,
    'HeartRate': 111,
    'BloodPressurePosition': 'Standing',
    'VitalSite': 'Popliteal',
    'VitalID': 1135,
    'Laterality': 'Right',
    'HeartRateRegularity': 'Regular',
    'HeadCircumference': '',
    'BloodPressureSystolic': 120,
    'CuffSize': 'XL'
}];

for (i=0; i < values.length; i++) {
        alert(values.length) // gives me 2. 

如何找到我的对象有多少个键？

Answer 1

var value = {
    'SPO2': 222.00000,
    'VitalGroupID': 1152,
    'Temperature': 36.6666666666667,
    'DateTimeTaken': '/Date(1301494335000-0400)/',
    'UserID': 1,
    'Height': 182.88,
    'UserName': null,
    'BloodPressureDiastolic': 80,
    'Weight': 100909.090909091,
    'TemperatureMethod': 'Oral',
    'Resprate': null,
    'HeartRate': 111,
    'BloodPressurePosition': 'Standing',
    'VitalSite': 'Popliteal',
    'VitalID': 1135,
    'Laterality': 'Right',
    'HeartRateRegularity': 'Regular',
    'HeadCircumference': '',
    'BloodPressureSystolic': 120,
    'CuffSize': 'XL'
};

alert(Object.keys(value).length);