如何检查密钥是否存在于json中

Question

我有JSON对象,我想检查在该JSON对象中设置的键

这是JSON对象

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18",
            "Child": [{
                "FromAge": "0",
                "ToAge": "12",
                "Price": "10"
            }]
        }
    }
}

如果JSON Object像这样你可以看到Child不存在,那么如何检查这个

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18"
        }
    }
}

我试过了

if(Data_Array.Private.Price.Child[0].Price != "undefined"){
    ...
}

但它告诉我这个错误

未捕获的TypeError:无法读取属性

我无法知道我该怎么做.

Answer 1

var json = {key1: 'value1', key2: 'value2'}

"key1" in json ? console.log('key exists') : console.log('unknown key')

"key3" in json ? console.log('key exists') : console.log('unknown key')

对于儿童钥匙

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18",
            "Child": [{
                "FromAge": "0",
                "ToAge": "12",
                "Price": "10"
            }]
        }
    }
}

'Child' in Data_Array.Private.Price ? console.log('Child detected') : console.log('Child missing')

创建变量子

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18",
            "Child": [{
                "FromAge": "0",
                "ToAge": "12",
                "Price": "10"
            }]
        }
    }
}

var child = 'Child' in Data_Array.Private.Price && Data_Array.Private.Price.Child[0] || 'there is no child'

console.log(child)

如果没有孩子

var Data_Array = {
    "Private": {
        "Price": {
            "Adult": "18"
        }
    }
}

var child = 'Child' in Data_Array.Private.Price && Data_Array.Private.Price.Child[0] || 'there is no child'

console.log(child)