如何访问带有列表的嵌套 json 中的数据？

Question

This has been a real pain for me and I can't solve it. I have a Json that looks like this:

"name": "The data",
"list": [
    {
        "item": "a613424",
        "locations": [
            {
                "name": "start",
                "a": 5.743,
                "b": 0.093
            }
        ]
    },
    {
        "item": "e88934",
        "locations": [
            {
                "name": "start",
                "a": 6.64,
                "b": 0.43
            }
        ]
    },
    {
        "item": "d92213",
        "locations": [
            {
                "name": "start",
                "a": 12.33,
                "b": 0.91
            },
            {
                "name": "stop",
                "a": 889,
                "b": 1.134
            }
        ]
    }]}

Every item has an item code, and in locations has a name and values for a and b. Some items have 2 names. I need to read through this and extract the item code, name(s) and a and b values. I don't know how many items will be in the json or which items will have multiple names.

I either get an object returned or 'unknown'

x = test_data.list[0]; document.write(x);

outputs [object object]

document.write(test_data[0]);

outputs 'undefined'

I could do this in 5 minutes in Python, but sadly this has to be in javascript.

Thanks

Answer 1

Access the lists through forEach and item and locations properties. It's easy since you have a constant structure for your JSON

 let data = { "name": "The data", "list": [{ "item": "a613424", "locations": [{ "name": "start", "a": 5.743, "b": 0.093 }] }, { "item": "e88934", "locations": [{ "name": "start", "a": 6.64, "b": 0.43 }] }, { "item": "d92213", "locations": [{ "name": "start", "a": 12.33, "b": 0.91 }, { "name": "stop", "a": 889, "b": 1.134 } ] } ] }; let listItems = data.list; listItems.forEach(item => { console.log("item code: " + item.item); // item code item.locations.forEach(location => { console.log("location a is: " + location.a); // a console.log("location b is: " + location.b); // b }); console.log("\n"); //for breakline });

Answer 2

 let objectData = { name: "The data", list: [ { item: "a613424", locations: [ { name: "start", a: 5.743, b: 0.093 } ] }, { item: "e88934", locations: [ { name: "start", a: 6.64, b: 0.43 } ] }, { item: "d92213", locations: [ { name: "start", a: 12.33, b: 0.91 }, { name: "stop", a: 889, b: 1.134 } ] } ] }; let obDList = objectData.list.map((x) => x.locations.map((y) => { return `a = ${ya}, b = ${yb} `; }) ); console.log(obDList); console.log(obDList[2][1]);