Operating on JSON objects/arrays according to their values

Question

Operating on JSON objects/arrays according to their values

I am working on developing a function that accepts a string as its first argument and a JSON LIST as its second argument:

[
    {
        "date": "09/09/18",
        "how_many": 11,
        "species": "XXXXX"
    },
    {
        "date": "04/11/17",
        "how_many": 41,
        "species": "TTTTTT"
    },
    {
        "date": "17/03/18",
        "how_many": 30,
        "species": "DDDDDDDD"
    },
    {
        "date": "17/08/18",
        "how_many": 31,
        "species": "XXXXX"
    },
]

If the input string matches with any of the values under "species" key in each JSON entry, it will calculate the number of occurrences.

In simple terms, I need to create a function that counts how many times the input string appears in the list of objects based on the value of the "species" key.

javascript json loops ecmascript-6

Answer 1

Answer №1

If you're looking to streamline your array manipulation, consider using the Array.reduce method.

The official documentation explains that reduce() applies a reducing function to each element in the array to produce a single output value:

The reduce() method executes a reducer function (which you define) on every item of the array, resulting in a final output value.

The value returned by your reducer function is added to an accumulator, which retains its value throughout the iterations and eventually becomes the ultimate resultant value.

EXPLANATION

By using the reduce function, you can condense an array into a single value, such as the sum of all matching species. The initial sum value is set to 0, and during iteration, the function checks if the object's species matches the provided value. If there's a match, it adds the how_many value to the total sum.

ES6

let list = [{"date":"09/09/18","how_many":11,"species":"XXXXX"},{"date":"04/11/17","how_many":41,"species":"TTTTTT"},{"date":"17/03/18","how_many":30,"species":"DDDDDDDD"},{"date":"17/08/18","how_many":31,"species":"XXXXX"}];

function findOccurences(str, arr) {
  return arr.reduce((a,c) => a + (c.species === str ? c.how_many : 0), 0);
}

console.log(findOccurences("XXXXX", list));

ES5

let list = [{"date":"09/09/18","how_many":11,"species":"XXXXX"},{"date":"04/11/17","how_many":41,"species":"TTTTTT"},{"date":"17/03/18","how_many":30,"species":"DDDDDDDD"},{"date":"17/08/18","how_many":31,"species":"XXXXX"}];

function findOccurences(str, arr) {
  // "a" represents the accumulator, "c" represents the current value
  return arr.reduce(function(a, c){
    // If the object's species matches the provided value ("str"), add its how_many value to the total sum
    if(c.species === str) {
      a += c.how_many;
    }
    return a;
  }, 0);
}

console.log(findOccurences("XXXXX", list));

Answer 2

If you're looking to streamline your array manipulation, consider using the Array.reduce method.

The official documentation explains that reduce() applies a reducing function to each element in the array to produce a single output value:

The reduce() method executes a reducer function (which you define) on every item of the array, resulting in a final output value.

The value returned by your reducer function is added to an accumulator, which retains its value throughout the iterations and eventually becomes the ultimate resultant value.

EXPLANATION

By using the reduce function, you can condense an array into a single value, such as the sum of all matching species. The initial sum value is set to 0, and during iteration, the function checks if the object's species matches the provided value. If there's a match, it adds the how_many value to the total sum.

ES6

let list = [{"date":"09/09/18","how_many":11,"species":"XXXXX"},{"date":"04/11/17","how_many":41,"species":"TTTTTT"},{"date":"17/03/18","how_many":30,"species":"DDDDDDDD"},{"date":"17/08/18","how_many":31,"species":"XXXXX"}];

function findOccurences(str, arr) {
  return arr.reduce((a,c) => a + (c.species === str ? c.how_many : 0), 0);
}

console.log(findOccurences("XXXXX", list));

ES5

let list = [{"date":"09/09/18","how_many":11,"species":"XXXXX"},{"date":"04/11/17","how_many":41,"species":"TTTTTT"},{"date":"17/03/18","how_many":30,"species":"DDDDDDDD"},{"date":"17/08/18","how_many":31,"species":"XXXXX"}];

function findOccurences(str, arr) {
  // "a" represents the accumulator, "c" represents the current value
  return arr.reduce(function(a, c){
    // If the object's species matches the provided value ("str"), add its how_many value to the total sum
    if(c.species === str) {
      a += c.how_many;
    }
    return a;
  }, 0);
}

console.log(findOccurences("XXXXX", list));

Answer 3

Answer №2

Give this a shot:

function getOccurrenceCount(inputStr, dataList) {
   var matchingItems = dataList.filter(item => item.type === inputStr);
   return matchingItems.length;
}

Answer 4

Give this a shot:

function getOccurrenceCount(inputStr, dataList) {
   var matchingItems = dataList.filter(item => item.type === inputStr);
   return matchingItems.length;
}

Operating on JSON objects/arrays according to their values

Answer №1

Answer №2

Similar questions

Exploring the functionalities of Express and Socket.io

What is the best way to transmit data as a reply from a Node.js server to an AJAX client?

Troubleshoot: jQuery Datalink functionality not functioning properly with object methods

Retrieve only ObjectIds that are embedded in an Array using MongoDB's .find() method

What exactly happens behind the scenes when JSON.stringify() is called?

The feature to disable legend click in Chart.js does not activate unless the specific condition is met

What is the best way to send a promise back from my service to my controller?

Retrieve a specific item from the JSON dataset

How can I properly choose distinct values for an individual attribute from a JavaScript array containing objects?

Encountering an Error When Trying to Read a JSON String: TypeError - string indices must be

When the request's credentials mode is set to 'include', the 'Access-Control-Allow-Origin' header in the response should not be using the wildcard '*'

Representation of data format obtained from a method for selecting an element with a data URL in JQGrid

Using Node.js, express, jade, highcharts, and a 2D array

Updating the innerHTML of a button with a specific id using Javascript is not possible due to it being "null."

Strategies for preserving context throughout an Ajax request

The identical page content is displayed on each and every URL

Tips for showing JSON results on an ASP.NET webpage retrieved from an SQL database

Reopen a Kendo UI dialog

Why is the useHistory hook in React failing to function properly?

Simple React application