Iterate through an array containing objects that may have optional properties, ensuring to loop through the entire

Question

Iterate through an array containing objects that may have optional properties, ensuring to loop through the entire

I need help iterating through an array of objects with a specific interface structure:

export interface Incident {
  ID: string;
  userName1?: string;
  userName2?: string;
  userPhoneNumber?: string;
  crashSeverity: number;
  crashTime: number;
}

Here is a sample data set:

  {
    crashID: "CO111111",
    userName1: "TEST",
    userName2: "NAME2",
    userPhoneNumber: "11111",
    crashSeverity: 2,
    crashTime: 1571566666
  },
  {
    crashID: "12345",
    userName1: "TEST",
    crashSeverity: 2,
    crashTime: 1571566666
  }

I want to save this data to a csv file, but I'm struggling with iterating through the entire incident interface for each object and handling missing properties. Is there a way to achieve this?

An example output can be seen here: https://i.sstatic.net/ByAHg.png

This is my current code snippet:


  ConvertToCSV(objArray) {
    const array =
      typeof objArray !== "object" ? JSON.parse(objArray) : objArray;
    let str = "";
    let header = "";

    for (const index in objArray[0]) {
      header += index + ";";
    }
    header = header.slice(0, -1);
    // append Label row with line break
    str += header + "\r\n";

    // loop through every entry
    for (let i = 0; i < array.length; i++) {
      let line = "";
      // loop through every row
      for (const firstIndex in array[i]) {
          line += array[i][firstIndex] + ";";
      }
      str += line + "\r\n";
    }
    return str;
  }

javascript arrays typescript interface

Answer 1

Answer №1

Interfaces are only present during compile time and do not exist at run-time, making it impossible to inspect them using code.

However, there are ways to ensure that the output CSV is properly formatted by examining the data and organizing the fields correctly. This involves analyzing all the data to determine which fields are used and creating a logical order for them. This process is similar to performing a topological sort.

The provided code accomplishes this task by first scanning and ordering the data, then encoding it into a CSV format. The function `convertToCSV` parses the object array, identifies field dependencies, performs a topological sort of the fields, and generates the CSV data accordingly.

This script demonstrates how to efficiently convert structured data into a well-organized CSV output:

function convertToCSV(objArray) {
    const array =
        typeof objArray === "string" ? JSON.parse(objArray) : objArray;
    
    // Iterate the whole array to find any fields
    //    Keep track of which fields have to precede other fields
    const predecessors = new Map;
    for (const obj of array) {
        Object.keys(obj).forEach((key, i, keys) => {
            if (!predecessors.has(key)) predecessors.set(key, new Set);
            if (i) predecessors.get(key).add(keys[i-1]);
        });
    }
    // Sort fields
    const fields = topologicalSort(predecessors);

    return [fields.join(";"), // header line
        ...array.map(obj => fields.map(field => obj[field] || "").join(";")) // data lines
    ].join("\r\n");
}

function topologicalSort(predecessors) {
    const visited = new Set;
    
    function visit(key) {
        if (visited.has(key)) return;
        predecessors.get(key).forEach(visit);
        visited.add(key);
    }
    
    for (let key of predecessors.keys()) visit(key);
    return [...visited];
}

// Sample data
const data = [{
    userName2: "NAME2",
    userPhoneNumber: "11111",
    crashSeverity: 2,
  }, {
    userName1: "TEST",
    crashSeverity: 2,
    crashTime: 1571577777
  }, {
    crashID: "12345",
    userName1: "Mr First",
    userName2: "Second name",
    crashSeverity: 3,
    crashTime: 1571588888
  }];

const csv = convertToCSV(data);
console.log(csv);

Answer 2

Interfaces are only present during compile time and do not exist at run-time, making it impossible to inspect them using code.

However, there are ways to ensure that the output CSV is properly formatted by examining the data and organizing the fields correctly. This involves analyzing all the data to determine which fields are used and creating a logical order for them. This process is similar to performing a topological sort.

The provided code accomplishes this task by first scanning and ordering the data, then encoding it into a CSV format. The function `convertToCSV` parses the object array, identifies field dependencies, performs a topological sort of the fields, and generates the CSV data accordingly.

This script demonstrates how to efficiently convert structured data into a well-organized CSV output:

function convertToCSV(objArray) {
    const array =
        typeof objArray === "string" ? JSON.parse(objArray) : objArray;
    
    // Iterate the whole array to find any fields
    //    Keep track of which fields have to precede other fields
    const predecessors = new Map;
    for (const obj of array) {
        Object.keys(obj).forEach((key, i, keys) => {
            if (!predecessors.has(key)) predecessors.set(key, new Set);
            if (i) predecessors.get(key).add(keys[i-1]);
        });
    }
    // Sort fields
    const fields = topologicalSort(predecessors);

    return [fields.join(";"), // header line
        ...array.map(obj => fields.map(field => obj[field] || "").join(";")) // data lines
    ].join("\r\n");
}

function topologicalSort(predecessors) {
    const visited = new Set;
    
    function visit(key) {
        if (visited.has(key)) return;
        predecessors.get(key).forEach(visit);
        visited.add(key);
    }
    
    for (let key of predecessors.keys()) visit(key);
    return [...visited];
}

// Sample data
const data = [{
    userName2: "NAME2",
    userPhoneNumber: "11111",
    crashSeverity: 2,
  }, {
    userName1: "TEST",
    crashSeverity: 2,
    crashTime: 1571577777
  }, {
    crashID: "12345",
    userName1: "Mr First",
    userName2: "Second name",
    crashSeverity: 3,
    crashTime: 1571588888
  }];

const csv = convertToCSV(data);
console.log(csv);

Answer 3

Answer №2

To tackle this issue, I implemented a method where I saved the headers within the .ts file and retrieved the values by referencing their respective header names:

headers = [
  "crashID",
  "userName1",
  "userName2",
  "userPhoneNumber",
  "crashSeverity",
  "crashTime"
];

convertToCSV(objArray) {
  const array =
    typeof objArray !== "object" ? JSON.parse(objArray) : objArray;
  let str = "";
  const header = this.headers.join(";");
  str += header + "\r\n";

  // iterate through each entry
  for (let i = 0; i < array.length; i++) {
    let line = "";
    // iterate through each row
    for (const headerElem of this.headers) {
      line += array[i][headerElem];
      line += ";";
    }
    str += line + "\r\n";
  }
  return str;
}

Answer 4

To tackle this issue, I implemented a method where I saved the headers within the .ts file and retrieved the values by referencing their respective header names:

headers = [
  "crashID",
  "userName1",
  "userName2",
  "userPhoneNumber",
  "crashSeverity",
  "crashTime"
];

convertToCSV(objArray) {
  const array =
    typeof objArray !== "object" ? JSON.parse(objArray) : objArray;
  let str = "";
  const header = this.headers.join(";");
  str += header + "\r\n";

  // iterate through each entry
  for (let i = 0; i < array.length; i++) {
    let line = "";
    // iterate through each row
    for (const headerElem of this.headers) {
      line += array[i][headerElem];
      line += ";";
    }
    str += line + "\r\n";
  }
  return str;
}

Iterate through an array containing objects that may have optional properties, ensuring to loop through the entire

Answer №1

Answer №2

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