Identify the following map based on the sequence in the mapsOrder array

Question

Identify the following map based on the sequence in the mapsOrder array

I have two arrays, mapsOrder and mapsData, containing objects:

let mapsOrder = [1,2,1,3];
let mapData = [
  {
    id: 1,
    gates: [
      {
        toId: 2,
        coords: {
          x: 2,
          y: 42
        }
      },
      {
        toId: 3,
        coords: {
          x: 9,
          y: 4
        }
      }
    ]
  },
  {
    id: 2,
    gates: [
      {
        toId: 1,
        coords: {
          x: 6,
          y: 5
        }
      }
    ]
  },
  {
    id: 3,
    gates: [
      {
        toId: 1,
        coords: {
          x: 2,
          y: 1
        }
      }
    ]
  }
]

The goal is to loop through the mapsOrder array where its values correspond to ids in mapData, and assign gates to the next map.

During each iteration:

When index is 1, current map is 1, next map is 2, and gates to next are coords: { x: 2, y: 42 }
When index is 2, current map is 2, next map is 1, and gates to next are coords: { x: 6, y: 5 }
When index is 3, current map is 1, next map is 3, and gates to next are coords: { x: 9, y: 4 }
When index is 4, current map is 3, next map is 1, and gates to next are coords: { x: 2, y: 1 }

For the last iteration, the next map will be the first one in the mapsOrder array. I attempted to achieve this by determining the id of the next map using the following code snippet:

for(let i = 0; i < mapsOrder.length; i++) {
  let nextMap;
  let currentMapId = mapData[mapsOrder[i] - 1].id;
  if(i === mapsOrder.length - 1) {
    nextMap = mapData[0].id   
  } else {
    nextMap = mapData[mapsOrder[i]].id;    
  }

  console.log('Current map is: ', currentMapId, 'and the next map id is:', nextMap)
  console.log('break-----')

}

However, this code returns incorrect IDs. You can view a live demo here.

javascript arrays algorithm

Answer 1

Answer №1

If you are not concerned about the original array, you can simply utilize `shift` to retrieve the next gate (since `shift` removes the gate from the array, making the next gate available when the object is encountered again). Use `find` to search for the object in the array:

let result = mapsOrder.map(id =>
    mapData.find(o => o.id == id).gates.shift().coords
);

It might be wise to verify if `find` actually locates something and if the gates array contains elements before applying `shift`. Here is a more cautious approach:

let result = mapsOrder.map(id => {
    let obj = mapData.find(o => o.id == id);
    if(obj && obj.gates.length) {                  // if an object with the specified id is found and it has gates
        return obj.gates.shift().coords;           // retrieve the coordinates of the first gate while removing it from the array
    }                                              // alternatively, handle the absence of gates
});

No modifications:

Rather than utilizing `shift` as shown previously, we will employ an object to monitor the gate index from the `gates` array:

let nextGateIndex = Object.create(null);                             // creating a prototypeless object to track the next gate index for each object
let result = mapsOrder.map(id => {
    let obj = mapData.find(o => o.id == id);
    let index;
    if(nextGateIndex[id] == undefined) {
        index = 0;
    } else {
        index = nextGateIndex[id] + 1;
    }
    nextGateIndex[id] = index;
    if(obj && index < obj.gates.length) {
        return obj.gates[index].coords;
    }                                                                // handle error or alternative path
});

Answer 2

If you are not concerned about the original array, you can simply utilize `shift` to retrieve the next gate (since `shift` removes the gate from the array, making the next gate available when the object is encountered again). Use `find` to search for the object in the array:

let result = mapsOrder.map(id =>
    mapData.find(o => o.id == id).gates.shift().coords
);

It might be wise to verify if `find` actually locates something and if the gates array contains elements before applying `shift`. Here is a more cautious approach:

let result = mapsOrder.map(id => {
    let obj = mapData.find(o => o.id == id);
    if(obj && obj.gates.length) {                  // if an object with the specified id is found and it has gates
        return obj.gates.shift().coords;           // retrieve the coordinates of the first gate while removing it from the array
    }                                              // alternatively, handle the absence of gates
});

No modifications:

Rather than utilizing `shift` as shown previously, we will employ an object to monitor the gate index from the `gates` array:

let nextGateIndex = Object.create(null);                             // creating a prototypeless object to track the next gate index for each object
let result = mapsOrder.map(id => {
    let obj = mapData.find(o => o.id == id);
    let index;
    if(nextGateIndex[id] == undefined) {
        index = 0;
    } else {
        index = nextGateIndex[id] + 1;
    }
    nextGateIndex[id] = index;
    if(obj && index < obj.gates.length) {
        return obj.gates[index].coords;
    }                                                                // handle error or alternative path
});

Answer 3

Answer №2

If you follow the description, your loop should look like this. It seems that you want to utilize id and toId, but in the context of array indexes. Consider replacing arrays with objects for a better approach.

Check out the demo here

for(let i = 0; i < mapsOrder.length; i++) {
  let nextMap;
  let currentMapId = mapsOrder[i];
  if(i === mapsOrder.length - 1) {
    nextMapId = mapsOrder[0]   
  } else {
    nextMapId = mapsOrder[i + 1];    
  }
  let filteredMapData = mapData.filter(f => f.id == currentMapId);
  let filteredGates = filteredMapData.length > 0 ? filteredMapData[0].gates.filter(f => f.toId == nextMapId) : [];

  console.log('Current map is: ', currentMapId, 'and the next map id is:', nextMapId, 'gates:', filteredGates.length == 0 ? "no gates": filteredGates[0].coords)
  console.log('break----')

}

Answer 4

If you follow the description, your loop should look like this. It seems that you want to utilize id and toId, but in the context of array indexes. Consider replacing arrays with objects for a better approach.

Check out the demo here

for(let i = 0; i < mapsOrder.length; i++) {
  let nextMap;
  let currentMapId = mapsOrder[i];
  if(i === mapsOrder.length - 1) {
    nextMapId = mapsOrder[0]   
  } else {
    nextMapId = mapsOrder[i + 1];    
  }
  let filteredMapData = mapData.filter(f => f.id == currentMapId);
  let filteredGates = filteredMapData.length > 0 ? filteredMapData[0].gates.filter(f => f.toId == nextMapId) : [];

  console.log('Current map is: ', currentMapId, 'and the next map id is:', nextMapId, 'gates:', filteredGates.length == 0 ? "no gates": filteredGates[0].coords)
  console.log('break----')

}

Answer 5

Answer №3

If you're working with JavaScript arrays, I highly recommend using the filter() function. It's incredibly efficient and will create a new array containing elements that meet specific criteria (such as objects with a desired id).

for (let i = 0; i < mapsOrder.length; i++) {
    console.log(mapData.filter(mapDataItem => mapDataItem.id === mapsOrder[i]))
}

Answer 6

If you're working with JavaScript arrays, I highly recommend using the filter() function. It's incredibly efficient and will create a new array containing elements that meet specific criteria (such as objects with a desired id).

for (let i = 0; i < mapsOrder.length; i++) {
    console.log(mapData.filter(mapDataItem => mapDataItem.id === mapsOrder[i]))
}

Identify the following map based on the sequence in the mapsOrder array

Answer №1

Answer №2

Answer №3

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