CODEWITHSUNDEEP
javascriptarrays
Laurent Trépanier
Laurent Trépanier

Reputation: 15

Create pairs out of an array of integers

I have this function that loops through some object properties.

It returns this:

Central Park: 0,1,1,1,2,1,3,1,4,1,5,1,6,1,7,1

Juniper Valley Park: 2,0

Highland Park: 2,0,5,0

var parks = [
{
    name: 'Central Park',
    landmarks: [[0,1],[1,1],[2,1],[3,1],[4,1],[5,1],[6,1],[7,1]]
},
{
    name: 'Juniper Valley Park',
    landmarks: [2,0]
},
{
    name: 'Highland Park',
    landmarks: [[2,0],[5,0]]
},]
function showLandmarks() {
 for (var i = 0, len = parks.length; i < len; i++) {
    console.log(parks[i].name +': '+parks[i].landmarks);
 }
}
showLandmarks();

I would like to create pairs out of the returned data. The expected result is:

Central Park: [[0,1],[1,1],[2,1],[3,1],[4,1],[5,1],[6,1],[7,1]]

Juniper Valley Park: [2,0]

Highland Park: [[2,0],[5,0]]

I found a few topics here but only partial information.

Upvotes: 0

Views: 84

Answers (6)

Keith
Keith

Reputation: 994

It's pretty difficult to manage through the Juniper entry since it isn't the same format, but the code below does the trick:

var parks = [
  {
    name: 'Central Park',
    landmarks: [[0,1],[1,1],[2,1],[3,1],[4,1],[5,1],[6,1],[7,1]]
  },
  {
    name: 'Juniper Valley Park',
    landmarks: [2,0]
  },
  {
    name: 'Highland Park',
    landmarks: [[2,0],[5,0]]
  }
];

function arrayToString(array) {
  return "[" + array.join(',') + "]";
}

function showLandmarks() {
  parks.forEach(function(park) {
    var landmarks = park.landmarks;
    if (!Array.isArray(landmarks[0])) {
      landmarks = [landmarks];
    }
    var row = landmarks.map(function(lm) {
      return arrayToString(lm);
    })
    var result = row.length > 1? "[" + row.join(",") + "]" : row.join(",");
    console.log(park.name + ':', result);
  })
}
showLandmarks();

Upvotes: 0

Sergio Belevskij
Sergio Belevskij

Reputation: 2957

remove JSON.stringify, if you don't need return a string instead of array of arrays. 

const landmarks = (...points) => {
  const result = [];
  while (points.length) {
    result.push(points.splice(0, 2));
  }
  return JSON.stringify(result);
};

// test
// Central Park:
console.log(landmarks(0, 1, 1, 1, 2, 1, 3, 1, 4, 1, 5, 1, 6, 1, 7, 1));
// Juniper Valley Park:
console.log(landmarks(2, 0));
// Highland Park:
console.log(landmarks(2, 0, 5, 0));

Upvotes: 0

Matthew Jenkins
Matthew Jenkins

Reputation: 1

You don't need to use a loop here you can use a forEach on the Array and not have to worry about the i index. This assumes for course that you always want the full array.

I suspect you actually want to have the [] printed around the coordinates. if so you can use map to add them to each coordinate set.

I would say that even though Juniper Valley Park only has one entry, that entry should still be within an Array for its own to keep data consistent.

{
    name: "Juniper Valley Park",
    landmarks: [[2, 0]]
  },

This means we won't need any special logic to handle cases with only one coordinate.

var parks = [
{
    name: 'Central Park',
    landmarks: [[0,1],[1,1],[2,1],[3,1],[4,1],[5,1],[6,1],[7,1]]
},
{
    name: 'Juniper Valley Park',
    landmarks: [[2,0]]
},
{
    name: 'Highland Park',
    landmarks: [[2,0],[5,0]]
},]
function showLandmarks() {
 parks.forEach(park => 
    console.log(park.name +': ['+ park.landmarks.map(landmark => '[' + landmark +']') + ']'));
 }
showLandmarks();

Output: Central Park: [0,1],[1,1],[2,1],[3,1],[4,1],[5,1],[6,1],[7,1]]

Juniper Valley Park: [[2,0]]

Highland Park: [[2,0],[5,0]]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/forEach https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map

Upvotes: 0

Code Maniac
Code Maniac

Reputation: 37775

When you use + between two objects it internally calls toString and changes than concate the converted string

console.log([1,2]+[3,4])

You can use Object.fromEntries

var parks = [{ name: 'Central Park',landmarks: [[0,1],[1,1],[2,1],[3,1],[4,1],[5,1],[6,1],[7,1]]},{    name: 'Juniper Valley Park',landmarks: [2,0]},{ name: 'Highland Park',landmarks: [[2,0],[5,0]]},]

let obj = Object.fromEntries(parks.map(({
  name,
  landmarks
}) => [name, landmarks]))

console.log(obj)

Upvotes: 0

jacob13smith
jacob13smith

Reputation: 929

Instead of incrementing i by one every loop, create a pair using parks[i] and parks[i+1] and add that pair to an accumulator array, then increment i by two.

You will just have to perform a check that parks[i+1] exists.

Upvotes: 0

Taki
Taki

Reputation: 17664

instead of manipulating the results, You could reduce the original array to an object : 

var parks = [
  {
    name: "Central Park",
    landmarks: [[0, 1], [1, 1], [2, 1], [3, 1], [4, 1], [5, 1], [6, 1], [7, 1]]
  },
  {
    name: "Juniper Valley Park",
    landmarks: [2, 0]
  },
  {
    name: "Highland Park",
    landmarks: [[2, 0], [5, 0]]
  }
];

const result = parks.reduce((acc, curr) => {
  acc[curr.name] = curr.landmarks;
  return acc;
}, {});

console.log(result);

Upvotes: 0

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