[英]Accessing and printing nested JSON object
我无法访问以下 object 中的嵌套键。 我正在尝试在“close_approach_data”内的“relative_velocity”中打印所有“kilometers_per_second”。
我得到一个错误,不明白我做错了什么。 先感谢您
const asteroidData = near_earth_objects
.map((data) => data.close_approach_data[0])
.map((e) => e.relative_velocity);
// TypeError: Cannot read property 'relative_velocity' of undefined
or
const asteroidData = near_earth_objects
.map((data) => data.close_approach_data[0].relative_velocity);
// TypeError: Cannot read property 'relative_velocity' of undefined
JSON object:
"near_earth_objects": [
{
"links": {
"self": "http://www.neowsapp.com/rest/v1/neo/2021277?api_key=24TE7EgNfmXIvdb6vNNZGBWx8s54XbZzCCi2oAdN"
},
"id": "2021277",
"neo_reference_id": "2021277",
"name": "21277 (1996 TO5)",
"designation": "21277",
"nasa_jpl_url": "http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2021277",
"absolute_magnitude_h": 16.1,
"estimated_diameter": {
"kilometers": {
"estimated_diameter_min": 1.6016033798,
"estimated_diameter_max": 3.5812940302
},
"meters": {
"estimated_diameter_min": 1601.6033797856,
"estimated_diameter_max": 3581.2940301941
},
"miles": {
"estimated_diameter_min": 0.9951898937,
"estimated_diameter_max": 2.2253122528
},
"feet": {
"estimated_diameter_min": 5254.6044325359,
"estimated_diameter_max": 11749.652706022
}
},
"is_potentially_hazardous_asteroid": false,
"close_approach_data": [
{
"close_approach_date": "1945-06-07",
"close_approach_date_full": "1945-Jun-07 22:35",
"epoch_date_close_approach": -775272300000,
"relative_velocity": {
"kilometers_per_second": "15.5094751879",
"kilometers_per_hour": "55834.1106763388",
"miles_per_hour": "34693.1450477507"
},
"miss_distance": {
"astronomical": "0.0334232973",
"lunar": "13.0016626497",
"kilometers": "5000054.084456751",
"miles": "3106889.5396991238"
},
"orbiting_body": "Mars"
}
],
"is_sentry_object": false
},
// Object continues repeating the above structure
您需要所有值还是只需要kilometers_per_second
值?
let near_earth_objects = [ { "links": { "self": "http://www.neowsapp.com/rest/v1/neo/2021277?api_key=24TE7EgNfmXIvdb6vNNZGBWx8s54XbZzCCi2oAdN" }, "id": "2021277", "neo_reference_id": "2021277", "name": "21277 (1996 TO5)", "designation": "21277", "nasa_jpl_url": "http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2021277", "absolute_magnitude_h": 16.1, "estimated_diameter": { "kilometers": { "estimated_diameter_min": 1.6016033798, "estimated_diameter_max": 3.5812940302 }, "meters": { "estimated_diameter_min": 1601.6033797856, "estimated_diameter_max": 3581.2940301941 }, "miles": { "estimated_diameter_min": 0.9951898937, "estimated_diameter_max": 2.2253122528 }, "feet": { "estimated_diameter_min": 5254.6044325359, "estimated_diameter_max": 11749.652706022 } }, "is_potentially_hazardous_asteroid": false, "close_approach_data": [ { "close_approach_date": "1945-06-07", "close_approach_date_full": "1945-Jun-07 22:35", "epoch_date_close_approach": -775272300000, "relative_velocity": { "kilometers_per_second": "15.5094751879", "kilometers_per_hour": "55834.1106763388", "miles_per_hour": "34693.1450477507" }, "miss_distance": { "astronomical": "0.0334232973", "lunar": "13.0016626497", "kilometers": "5000054.084456751", "miles": "3106889.5396991238" }, "orbiting_body": "Mars" } ], "is_sentry_object": false }]; let result = near_earth_objects.flatMap(({close_approach_data }) => close_approach_data.map(({relative_velocity})=> relative_velocity.kilometers_per_second)); console.log(result);
你的代码很好,只需要转换原始 json "near_earth_objects"
例子
const near_earth_objects = JSON.parse(JSON.stringify('YOUR_NEAR_EARTH')).near_earth_objects;
const asteroidData = near_earth_objects
.map((data) => data.close_approach_data[0].relative_velocity);
检查这个
const near_earth_objects_json = { "near_earth_objects": [ { "links": { "self": "http://www.neowsapp.com/rest/v1/neo/2021277?api_key=24TE7EgNfmXIvdb6vNNZGBWx8s54XbZzCCi2oAdN" }, "id": "2021277", "neo_reference_id": "2021277", "name": "21277 (1996 TO5)", "designation": "21277", "nasa_jpl_url": "http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2021277", "absolute_magnitude_h": 16.1, "estimated_diameter": { "kilometers": { "estimated_diameter_min": 1.6016033798, "estimated_diameter_max": 3.5812940302 }, "meters": { "estimated_diameter_min": 1601.6033797856, "estimated_diameter_max": 3581.2940301941 }, "miles": { "estimated_diameter_min": 0.9951898937, "estimated_diameter_max": 2.2253122528 }, "feet": { "estimated_diameter_min": 5254.6044325359, "estimated_diameter_max": 11749.652706022 } }, "is_potentially_hazardous_asteroid": false, "close_approach_data": [ { "close_approach_date": "1945-06-07", "close_approach_date_full": "1945-Jun-07 22:35", "epoch_date_close_approach": -775272300000, "relative_velocity": { "kilometers_per_second": "15.5094751879", "kilometers_per_hour": "55834.1106763388", "miles_per_hour": "34693.1450477507" }, "miss_distance": { "astronomical": "0.0334232973", "lunar": "13.0016626497", "kilometers": "5000054.084456751", "miles": "3106889.5396991238" }, "orbiting_body": "Mars" } ], "is_sentry_object": false }, { "links": { "self": "http://www.neowsapp.com/rest/v1/neo/2021277?api_key=24TE7EgNfmXIvdb6vNNZGBWx8s54XbZzCCi2oAdN" }, "id": "2021277", "neo_reference_id": "2021277", "name": "21277 (1996 TO5)", "designation": "21277", "nasa_jpl_url": "http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2021277", "absolute_magnitude_h": 16.1, "estimated_diameter": { "kilometers": { "estimated_diameter_min": 1.6016033798, "estimated_diameter_max": 3.5812940302 }, "meters": { "estimated_diameter_min": 1601.6033797856, "estimated_diameter_max": 3581.2940301941 }, "miles": { "estimated_diameter_min": 0.9951898937, "estimated_diameter_max": 2.2253122528 }, "feet": { "estimated_diameter_min": 5254.6044325359, "estimated_diameter_max": 11749.652706022 } }, "is_potentially_hazardous_asteroid": false, "close_approach_data": [ { "close_approach_date": "1945-06-07", "close_approach_date_full": "1945-Jun-07 22:35", "epoch_date_close_approach": -775272300000, "relative_velocity": { "kilometers_per_second": "15.5094751879", "kilometers_per_hour": "55834.1106763388", "miles_per_hour": "34693.1450477507" }, "miss_distance": { "astronomical": "0.0334232973", "lunar": "13.0016626497", "kilometers": "5000054.084456751", "miles": "3106889.5396991238" }, "orbiting_body": "Mars" } ], "is_sentry_object": false } ] } const near_earth_objects = JSON.parse(JSON.stringify(near_earth_objects_json)).near_earth_objects; const asteroidData = near_earth_objects.map((data) => data.close_approach_data[0].relative_velocity); console.log(asteroidData);
如果你只想要kilometers_per_second
,你可以这样做
const asteroidData = near_earth_objects
.map((data) => data.close_approach_data[0].relative_velocity.kilometers_per_second);
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