javascript assign array to object key

Question

javascript assign array to object key

Looking at this basic array:

const arr = [
  {
    "id": 2,
    "color": "red"
  },
  {
    "id": 1,
    "color": "blue"
  },
  {
    "id": 2,
    "color": "yellow"
  },
];

I am interested in constructing a hash map to update existing colors for each key.

For example, I want to add color: green to id: 3

Currently, there is no id: 3 present in the array

The expected outcome is as follows:

{
    2: [{color: "red"}]
    1: [{color: "blue"}, {color: "yellow"}],
    3: [{color: "green"}]
}

If I decide to include color: brown to id: 2

In such a scenario, I anticipate the following result:

{
    2: [{color: "red"}, {color: "brown"}]
    1: [{color: "blue"}, {color: "yellow"}],
    3: [{color: "green"}]
}

A Playground demonstration has been set up:

const arr = [
  {
    "id": 2,
    "color": "red"
  },
  {
    "id": 1,
    "color": "blue"
  },
  {
    "id": 2,
    "color": "yellow"
  },
];

function addItem(id: number, colors: any) {
    let newArr = {[id]: colors};
  arr.forEach(function (obj) {

    newArr[obj.id].push({id: obj.color});
  });
  return newArr;
}

console.log(addItem(3, [{color: "green"}]))
console.log(addItem(1, [{color: "brown"}]))

Additionally, duplicate entries should be avoided

javascript arrays typescript hashmap

Answer 1

Answer №1

const arr = [{
    "id": 2,
    "color": "red"
  },
  {
    "id": 1,
    "color": "blue"
  },
  {
    "id": 2,
    "color": "yellow"
  },
];

const groupedColors = arr.reduce((groups, current) => {
  if (!(current.id in groups)) {
    groups[current.id] = []
  }
  groups[current.id].push({
    color: current.color
  })
  return groups
}, {})

addNewItem(3, {
  color: "green"
})

addNewItem(1, {
  color: "brown"
})

console.log(groupedColors)

function addNewItem(id, item) {
  if (!(id in groupedColors)) {
    groupedColors[id] = []
  }
  groupedColors[id].push(item)
}

Answer 2

const arr = [{
    "id": 2,
    "color": "red"
  },
  {
    "id": 1,
    "color": "blue"
  },
  {
    "id": 2,
    "color": "yellow"
  },
];

const groupedColors = arr.reduce((groups, current) => {
  if (!(current.id in groups)) {
    groups[current.id] = []
  }
  groups[current.id].push({
    color: current.color
  })
  return groups
}, {})

addNewItem(3, {
  color: "green"
})

addNewItem(1, {
  color: "brown"
})

console.log(groupedColors)

function addNewItem(id, item) {
  if (!(id in groupedColors)) {
    groupedColors[id] = []
  }
  groupedColors[id].push(item)
}

Answer 3

Answer №2

function addColorToId(id, color) {
                for (var i = 0; i < array.length; i++) {
                  if (array[i].id == id) {
                    array[i].color.push(color)
                  }
                }
              }

This function loops through the provided array and adds a specific color to the element with matching id.

Answer 4

function addColorToId(id, color) {
                for (var i = 0; i < array.length; i++) {
                  if (array[i].id == id) {
                    array[i].color.push(color)
                  }
                }
              }

This function loops through the provided array and adds a specific color to the element with matching id.

Answer 5

Answer №3

Below is a code snippet that offers a solution to the given problem

const hashMap = new Map([
  [1, [{ color: "red" }]],
  [2, [{ color: "blue" }]],
  [3, [{ color: "yellow" }]],
]);

function addItem(id, colors) {
  hashMap.set(
    id,
    hashMap.has(id) ? [...hashMap.get(id).concat(colors)] : colors
  );

  return hashMap;
}
console.log(hashMap);
console.log(addItem(3, [{ color: "green" }]));
console.log(addItem(4, [{ color: "pink" }]));

Answer 6

Below is a code snippet that offers a solution to the given problem

const hashMap = new Map([
  [1, [{ color: "red" }]],
  [2, [{ color: "blue" }]],
  [3, [{ color: "yellow" }]],
]);

function addItem(id, colors) {
  hashMap.set(
    id,
    hashMap.has(id) ? [...hashMap.get(id).concat(colors)] : colors
  );

  return hashMap;
}
console.log(hashMap);
console.log(addItem(3, [{ color: "green" }]));
console.log(addItem(4, [{ color: "pink" }]));

Answer 7

Answer №4

let itemsArray = [{
          "id": 2,
          "color": "red"
        },
        {
          "id": 1,
          "color": "blue"
        },
        {
          "id": 2,
          "color": "yellow"
        },
      ];
      
      const groupItemsByColor = (items, key) => {
        return items.reduce(function(result, item) {
          const temp = {...item};
          delete temp[key];
          (result[item[key]] = result[item[key]] || []).push(temp);
          return result
        }, {})
      }
      
      const addNewItem = (id, colors) => {
        // const newItemsArray = itemsArray... etc if you do not want to alter the original array
        itemsArray = itemsArray.concat(colors.map(c => {
          c.id = id;
          return c
        }))
      
        const groupedItems = groupItemsByColor(itemsArray, 'id')
        return groupedItems
      }
      
      console.log(addNewItem(3, [{
        color: "green"
      }]))
      console.log(addNewItem(1, [{
        color: "brown"
      }]))

Answer 8

let itemsArray = [{
          "id": 2,
          "color": "red"
        },
        {
          "id": 1,
          "color": "blue"
        },
        {
          "id": 2,
          "color": "yellow"
        },
      ];
      
      const groupItemsByColor = (items, key) => {
        return items.reduce(function(result, item) {
          const temp = {...item};
          delete temp[key];
          (result[item[key]] = result[item[key]] || []).push(temp);
          return result
        }, {})
      }
      
      const addNewItem = (id, colors) => {
        // const newItemsArray = itemsArray... etc if you do not want to alter the original array
        itemsArray = itemsArray.concat(colors.map(c => {
          c.id = id;
          return c
        }))
      
        const groupedItems = groupItemsByColor(itemsArray, 'id')
        return groupedItems
      }
      
      console.log(addNewItem(3, [{
        color: "green"
      }]))
      console.log(addNewItem(1, [{
        color: "brown"
      }]))

Answer 9

Answer №5

Utilizing a class to encapsulate your data can be advantageous in this scenario.

Upon initialization, convert your array of objects into a Map with array values (an object can also be used as an alternative).
Develop a method that adds new colors to the appropriate map array only if they are not duplicates.

const arr=[{id:2,color:"red"},{id:1,color:"blue"},{id:2,color:"yellow"}];

class ColorMap {
        
  // `reduce` over the array to create a `colors` Map.
  // If the id doesn't exist on the map as a key,
  // create it, and assign an empty array to it.
  // Then push in the color to the array if
  // it doesn't already exist
  constructor(arr) {
    this.colors = arr.reduce((acc, obj) => {
      const { id, color } = obj;
      if (!acc.has(id)) acc.set(id, []);
      if (!this.colorExists(id, color)) {
        acc.get(id).push({ color });
      }
      return acc;
    }, new Map());
  }
  
  // Simple check to see if the color already
  // exists in the target array
  colorExists(id, color) {
    return this.colors?.get(id)?.find(obj => {
      return obj.color === color;
    });
  }

  // Similar to the `reduce` function, if the id doesn't have
  // a key on the map create one, and initialise an empty array,
  // and if the color doesn't already exist add it
  addColor(id, color) {
    if (!this.colors.has(id)) this.colors.set(id, []);
    if (!this.colorExists(id, color)) {
      this.colors.get(id).push({ color });
    }
  }

  // Return the colors map as a readable object
  showColors() {
    return Object.fromEntries(this.colors);
  }

}

const colorMap = new ColorMap(arr);

colorMap.addColor(3, 'green');
colorMap.addColor(1, 'brown');
colorMap.addColor(1, 'brown');

console.log(colorMap.showColors());

For more information, refer to the following documentation:

Answer 10

Utilizing a class to encapsulate your data can be advantageous in this scenario.

Upon initialization, convert your array of objects into a Map with array values (an object can also be used as an alternative).
Develop a method that adds new colors to the appropriate map array only if they are not duplicates.

const arr=[{id:2,color:"red"},{id:1,color:"blue"},{id:2,color:"yellow"}];

class ColorMap {
        
  // `reduce` over the array to create a `colors` Map.
  // If the id doesn't exist on the map as a key,
  // create it, and assign an empty array to it.
  // Then push in the color to the array if
  // it doesn't already exist
  constructor(arr) {
    this.colors = arr.reduce((acc, obj) => {
      const { id, color } = obj;
      if (!acc.has(id)) acc.set(id, []);
      if (!this.colorExists(id, color)) {
        acc.get(id).push({ color });
      }
      return acc;
    }, new Map());
  }
  
  // Simple check to see if the color already
  // exists in the target array
  colorExists(id, color) {
    return this.colors?.get(id)?.find(obj => {
      return obj.color === color;
    });
  }

  // Similar to the `reduce` function, if the id doesn't have
  // a key on the map create one, and initialise an empty array,
  // and if the color doesn't already exist add it
  addColor(id, color) {
    if (!this.colors.has(id)) this.colors.set(id, []);
    if (!this.colorExists(id, color)) {
      this.colors.get(id).push({ color });
    }
  }

  // Return the colors map as a readable object
  showColors() {
    return Object.fromEntries(this.colors);
  }

}

const colorMap = new ColorMap(arr);

colorMap.addColor(3, 'green');
colorMap.addColor(1, 'brown');
colorMap.addColor(1, 'brown');

console.log(colorMap.showColors());

For more information, refer to the following documentation:

javascript assign array to object key

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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