如何在多级数组中选择对象

Question

我试图得到标签下的微笑数组，然后是属性。我已经尝试了搜索和简单选择。每次尝试都会产生一个未定义的变量。如果你能解释如何选择微笑数组，那将是非常好的！

   {
        "status": "success",
        "photos": [{
            "url": "http://tinyurl.com/673cksr",
            "pid": "F@019cbdb135cff0880096136c4a0b9bad_3547b9aba738e",
            "width": 375,
            "height": 406,
            "tags": [{
                "uids": [],
                "label": null,
                "confirmed": false,
                "manual": false,
                "width": 30.67,
                "height": 28.33,
                "yaw": -16,
                "roll": -1,
                "pitch": 0,
                "attributes": {
                    "face": {
                        "value": "true",
                        "confidence": 84
                    },
                    "smiling": {
                        "value": "false",
                        "confidence": 46
                    }
                },
                "points": null,
                "similarities": null,
                "tid": "TEMP_F@019cbdb135cff0880096136c00d500a7_3547b9aba738e_56.80_41.13_0_1",
                "recognizable": true,
                "center": {
                    "x": 56.8,
                    "y": 41.13
                },
                "eye_left": {
                    "x": 66.67,
                    "y": 35.71,
                    "confidence": 51,
                    "id": 449
                },
                "eye_right": {
                    "x": 50.67,
                    "y": 35.47,
                    "confidence": 57,
                    "id": 450
                },
                "mouth_center": {
                    "x": 60.8,
                    "y": 51.23,
                    "confidence": 53,
                    "id": 615
                },
                "nose": {
                    "x": 62.4,
                    "y": 42.61,
                    "confidence": 54,
                    "id": 403
                }
            }]
        }],
        "usage": {
            "used": 21,
            "remaining": 79,
            "limit": 100,
            "reset_time": 1390111833,
            "reset_time_text": "Sun, 19 January 2014 06:10:33 +0000"
        },
        "operation_id": "edc2f994cd8c4f45b3bc5632fdb27824"
    }

Answer 1

JSON.parse(json).photos[0].tags[0].attributes.smiling

Answer 2

这段特定的代码将聚合来自给定对象的所有smiling属性，并将其作为数组返回。

• map函数将从每个标记中获取smiling属性。
• concat函数将扁平所有属性，并返回每个照片的一个数组。
• reduce函数将收集所有属性、所有照片并在result中积累结果，并在最后返回。

var result = data.photos.reduce(function(result, currentPhoto) {
    return result.concat(currentPhoto.tags.map(function(currentTag) {
        return currentTag.attributes.smiling;
    }));
}, []);

console.log(result);

输出

[ { value: 'false', confidence: 46 } ]

Answer 3

obj.photos[0].tags[0].attributes.smiling

最好的方法是循环遍历标记，而不是在那里硬编码0。

obj.photos.forEach(function(photo){
  photo.tags.forEach(function(tag){ 
    tag.attributes.smiling; // here it is
  });
});