Retrieve data from one array using information from another array. Alternatively, merging the arrays could also be a solution

Question

Retrieve data from one array using information from another array. Alternatively, merging the arrays could also be a solution

Welcome, developers, hackers, and watchers!

I'm facing an issue that I can't quite wrap my head around, specifically the part where I need to extract data from one array based on another.

Would merging them help?

Let's take a look at the two arrays:

var teams = ["red", "red", "red", "red", "blue", "blue"];
var scores = [4, 45, 21, 34, 76, 56];

var scoreRed = [];
var scoreBlue = [];

var i;
var scoreBlueIndex;
for (i = 0; i < teams.length; i++){
  scoreBlueIndex = teams.indexOf("blue");
  scoreBlue = scores[scoreBlueIndex];
}

var ii;
var scoreRedIndex;
for (ii = 0; ii < teams.length; ii++){
  scoreRedIndex = teams.indexOf("red");
  scoreRed = scores[scoreRedIndex];
}


console.log(scoreRed);
console.log(scoreBlue);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>

javascript arrays merge

Answer 1

Answer №1

By utilizing an object literal and Array.reduce method, you can achieve something like this ->

var teams = ["red", "red", "red", "red", "blue", "blue"];
var scores = [4, 45, 21, 34, 76, 56];

var results = teams.reduce((a,c,i) => {
  return (a[c] = (a[c] || 0) + scores[i]) && a;
}, {});

console.log(`Red: ${results.red}`);
console.log(`Blue: ${results.blue}`);

return (a[c] = (a[c] || 0) + scores[i]) && a;

The code above may appear complicated at first, but it becomes easier to understand with practice. Initially, the variables passed to this a,c,i represent the accumulator, currentValue, and currentIndex in the reduce function. For more information on reduce, visit -> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce?v=a

a[c] =, This is where we define the object literal, where c can be either blue or red, resulting in a["red"] = or a["blue"] =

a[c] || 0 accounts for the case where the object literal doesn't exist yet, setting the value to 0.

Lastly, we add the current score using i as the index value of the array, accessing the score. score[i].

The && a at the end -> When using reduce, the typical return value is the accumulator, thus (formula) && a ensures it always returns a. This serves as a shortcut to avoid an additional return a line.

Answer 2

By utilizing an object literal and Array.reduce method, you can achieve something like this ->

var teams = ["red", "red", "red", "red", "blue", "blue"];
var scores = [4, 45, 21, 34, 76, 56];

var results = teams.reduce((a,c,i) => {
  return (a[c] = (a[c] || 0) + scores[i]) && a;
}, {});

console.log(`Red: ${results.red}`);
console.log(`Blue: ${results.blue}`);

return (a[c] = (a[c] || 0) + scores[i]) && a;

The code above may appear complicated at first, but it becomes easier to understand with practice. Initially, the variables passed to this a,c,i represent the accumulator, currentValue, and currentIndex in the reduce function. For more information on reduce, visit -> https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce?v=a

a[c] =, This is where we define the object literal, where c can be either blue or red, resulting in a["red"] = or a["blue"] =

a[c] || 0 accounts for the case where the object literal doesn't exist yet, setting the value to 0.

Lastly, we add the current score using i as the index value of the array, accessing the score. score[i].

The && a at the end -> When using reduce, the typical return value is the accumulator, thus (formula) && a ensures it always returns a. This serves as a shortcut to avoid an additional return a line.

Answer 3

Answer №2

Incorrectly, the variables scoreRed and scoreBlue have been declared as arrays when they are meant to be scalar variables. Look at the corrected code snippet below:

var teams = ["red", "red", "red", "red", "blue", "blue"];
var scores = [4, 45, 21, 34, 76, 56];

var scoreRed=0;
var scoreBlue=0;

var i;
var scoreBlueIndex;
for (i = 0; i < teams.length; i++){
  scoreBlueIndex = teams.indexOf("blue", i);
  if(scoreBlueIndex > -1) {
    scoreBlue = scoreBlue + scores[scoreBlueIndex];
    i=scoreBlueIndex;
   }
   else break;
}

var ii;
var scoreRedIndex;
for (ii = 0; ii < teams.length; ii++){
  scoreRedIndex = teams.indexOf("red", ii);
  if(scoreRedIndex > -1) {
     scoreRed = scoreRed + scores[scoreRedIndex];
     ii=scoreRedIndex;
  }
  else break;
}


console.log(scoreRed);
console.log(scoreBlue);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>

Answer 4

Incorrectly, the variables scoreRed and scoreBlue have been declared as arrays when they are meant to be scalar variables. Look at the corrected code snippet below:

var teams = ["red", "red", "red", "red", "blue", "blue"];
var scores = [4, 45, 21, 34, 76, 56];

var scoreRed=0;
var scoreBlue=0;

var i;
var scoreBlueIndex;
for (i = 0; i < teams.length; i++){
  scoreBlueIndex = teams.indexOf("blue", i);
  if(scoreBlueIndex > -1) {
    scoreBlue = scoreBlue + scores[scoreBlueIndex];
    i=scoreBlueIndex;
   }
   else break;
}

var ii;
var scoreRedIndex;
for (ii = 0; ii < teams.length; ii++){
  scoreRedIndex = teams.indexOf("red", ii);
  if(scoreRedIndex > -1) {
     scoreRed = scoreRed + scores[scoreRedIndex];
     ii=scoreRedIndex;
  }
  else break;
}


console.log(scoreRed);
console.log(scoreBlue);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.8.0/jquery.min.js"></script>

Retrieve data from one array using information from another array. Alternatively, merging the arrays could also be a solution

Answer №1

Answer №2

Similar questions

Adjust the field of view of the camera in ThreeJS

What is the method for copying table data, including input text as cells, to the clipboard without using jQuery?

The checkbox is not updating as anticipated

Is it possible to modify the value of just one element within a Nested JSON in Kotlin?

Could Ramda assist in enhancing pipeline/composition processes with a logging feature?

Having trouble debugging the current TypeScript file in VS Code because the corresponding JavaScript file is missing

How can one utilize a second drop-down list in asp.net to alter the selected index and visibility of a drop-down list?

Console Error: Attempting to set the 'className' property of null object results in an

Display a set of JSON objects on separate lines rather than consolidating them on a single line

My redirect is being disrupted by passing a text string with new lines through GET requests

Difficulty in understanding sentences in the C language

Typescript Angular2 filtering tutorial

Include an external JavaScript file within a component to display pictures in a web browser using Angular 2

The Laravel function is not returning as expected on the server

Disabling the search function when it is clicked (before any actions are taken)

I am noticing that my popover is causing my page to shift when I click it. It is expanding the width of my page more than I would

PHP - JSON does not create any output

Add new data to an existing array in Angular 7 without overwriting it

Is it possible to implement PortalVue in multiple Vue.js single file components?

Sharing information between controllers while being initiated using $rootScope.$emit