How do I parse a JSON file with nested objects using JS?-CodePudding

I am very new to JavaScript and have been given the task of converting various JSON files into excel spreadsheets. I am having trouble understanding how to parse a JSON file that has nested objects or nested arrays. Please forgive me if I am not using the right wording. The following is a sample of the JSON data I need to parse.

  [{
        "name": "Kindergarten",
        "subject": "Math",
        "framework": "NC:  Standard Course of Study",
        "standards": [
            {
                "id": 1306687,
                "name": "NC.K.CC.1",
                "short_description": "Standard 1."
            },
            {
                "id": 1306688,
                "name": "NC.K.CC.1.a",
                "short_description": "Standard 2."
            },
            {
                "id": 1306689,
                "name": "NC.K.CC.1.b",
                "short_description": "Standard 3."
            }
           
        ]
    }]

I have tried so many different loops and can only seem to parse the first part of the file and not the nested part. I basically need the data to look like this when it's done:

    name    subject framework   standards/0/id  standards/0/name    standards/0/short_description
    Kindergarten    Math    NC:  Standard Course of Study   1306687 NC.K.CC.1   Standard 1.
    Kindergarten    Math    NC:  Standard Course of Study   1306688 NC.K.CC.1.a Standard 2.
    Kindergarten    Math    NC:  Standard Course of Study   1306689 NC.K.CC.1.b Standard 3.

Any guidance you can give will be immensely helpful.

CodePudding user response：

Simply use JSON.parse("<your JSON string>") for parsing. This function returns an object tree reflecting the processed JSON. Then you can access all object properties in your loop and generate a CSV file, which can be opened with Excel.

let csv = "";

const objects = JSON.parse("<your JSON string>");
for (const o of objects) {
  for (const std of o.standards) {
    csv  = `${o.name},${o.subject},${o.framework},${std.id},${std.name},${std.short_description}`;
  }
}

Working example:

const jsonData = `[{
  "name": "Kindergarten",
  "subject": "Math",
  "framework": "NC:  Standard Course of Study",
  "standards": [{
      "id": 1306687,
      "name": "NC.K.CC.1",
      "short_description": "Standard 1."
    },
    {
      "id": 1306688,
      "name": "NC.K.CC.1.a",
      "short_description": "Standard 2."
    },
    {
      "id": 1306689,
      "name": "NC.K.CC.1.b",
      "short_description": "Standard 3."
    }
  ]
}]`;

/* Escapes all quotes in the input in order to not break the CSV */
function val(input) {
  return input?.replaceAll ? input.replaceAll('"', '""') : input;
}

let csv = "";

const objects = JSON.parse(jsonData);
for (const o of objects) {
  for (const std of o.standards) {
    csv  = `"${val(o.name)}","${val(o.subject)}","${val(o.framework)}","${val(std.id)}","${val(std.name)}","${val(std.short_description)}"`;
  }
}

console.log(csv);

EDIT: Modified the source code to generate more save CSV (now double-quotes and commas are allowed in the input). Thanks to @phuzi!

CodePudding user response：

try this;

var data = [{
    "name": "Kindergarten",
    "subject": "Math",
    "framework": "NC:  Standard Course of Study",
    "standards": [
        {
            "id": 1306687,
            "name": "NC.K.CC.1",
            "short_description": "Standard 1."
        },
        {
            "id": 1306688,
            "name": "NC.K.CC.1.a",
            "short_description": "Standard 2."
        },
        {
            "id": 1306689,
            "name": "NC.K.CC.1.b",
            "short_description": "Standard 3."
        }
       
    ]
}]

const custom = [];
data.forEach((element)=>{
  const {name, subject,framework} = element;
  element.standards.forEach((elementInner)=>{
  const {id , name : stdName,short_description} = elementInner;
    custom.push({name, subject,framework, id, stdName, short_description});
  });
});
console.log(custom);

CodePudding user response：

You have a document:

let doc= '[{
    "name": "Kindergarten",
    "subject": "Math",
    "framework": "NC:  Standard Course of Study",
    "standards": 
    [
        {
            "id": 1306687,
            "name": "NC.K.CC.1",
            "short_description": "Standard 1."
        },
        {
            "id": 1306688,
            "name": "NC.K.CC.1.a",
            "short_description": "Standard 2."
        },
        {
            "id": 1306689,
            "name": "NC.K.CC.1.b",
            "short_description": "Standard 3."
        }           
    ]
}]'

Parse to a json object with JSON.parse(doc) Then you can iterate over the JSON array with "Nested For Loops":

let data = JSON.parse(doc);
for (let i =0; i < data.length; i  )
{
    for(let j = 0; j < data[i].standards.length; j  )
    {
        // obviously you aren't logging to console but for purposes of the demonstration I will
        console.log(`${data[i].name},${data[i].subject},${data[i].framework},${data[i].standards[j].id},${data[i].standards[j].name},${data[i].standards[j].short_description}`);
    }
}