how to merge two arrays of objects in javascript?-CodePudding

here is a sample example where there are two arrays and we have a merge() to which we pass the arrays. the merge() should return the merged array such that it should merge the objects which have same name.

let arr1 = [
  {
    name: "Person1",
    age: 20
  },
  {
    name: "Person2",
    age: 30
  }
]


let arr2 = [
  {
    name: "Person1",
    email: "[email protected]"
  },
  {
    name: "Person3",
    age: 25
  }
]


arr3 = merge(arr1, arr2)

output : 
arr3 should be : 
[
 {
    name: "Person1",
    age: 20,
    email: "[email protected]"
  },
   {
    name: "Person2",
    age: 30
  },
   {
    name: "Person3",
    age: 25
  }
]

CodePudding user response：

You could take an object as hash table for keeping track of merged objects with same name and return only the values from the hash table.

const
    merge = (...arrays) => {
        const merged = {};
        
        arrays.forEach(data =>
            data.forEach(o => Object.assign(merged[o.name] ??= {}, o))
        );
        
        return Object.values(merged);
    },
    array1 = [{ name: "Person1", age: 20 }, { name: "Person2", age: 30 }],
    array2 = [{name: "Person1", email: "[email protected]" }, { name: "Person3", age: 25 }],
    result = merge(array1, array2);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

CodePudding user response：

You can use lodash for that

let arr1 = [
  {
    name: "Person1",
    age: 20
  },
  {
    name: "Person2",
    age: 30
  }
]


let arr2 = [
  {
    name: "Person1",
    email: "[email protected]"
  },
  {
    name: "Person3",
    age: 25
  }
]


arr3 = _.merge(_.keyBy(arr1, 'name'), _.keyBy(arr2, 'name'));

console.log(arr3)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.min.js"></script>

CodePudding user response：

The map part covers every item in arr1, so you can add it as is or merge with the ones both in arr1 and arr2. Then you need a final pass to add those that are in arr2 but not in arr1

let arr1 = [
  {
    name: "Person1",
    age: 20
  },
  {
    name: "Person2",
    age: 30
  }
]


let arr2 = [
  {
    name: "Person1",
    email: "[email protected]"
  },
  {
    name: "Person3",
    age: 25
  }
]

const merge = (a1,a2) => {

return a1.map( (x) => {
  const y = a2.find( item => x.name === item.name);
  if (y) {
    return Object.assign({},x,y);
  } else
    return x
}).concat(a2.filter(item => a1.every( x => x.name !== item.name)));




}

arr3 = merge(arr1, arr2)

console.log(arr3)

CodePudding user response：

We can convert the arrays into objects for better time complexity and merge them using a spread operator and generate the array at the end.

let arr1 = [
  {
    name: "Person1",
    age: 20
  },
  {
    name: "Person2",
    age: 30
  }
]


let arr2 = [
  {
    name: "Person1",
    email: "[email protected]"
  },
  {
    name: "Person3",
    age: 25
  }
]
function merge(arr1, arr2){
  const merged_dict = {}
  const r_arr = []
  const arr = [...arr1,...arr2]
  arr.forEach(ele => {
    if(merged_dict[ele.name]){
      merged_dict[ele.name] = {...merged_dict[ele.name],...ele};
    }
    else{
      merged_dict[ele.name] = ele;
    }
  });
  for(let key in merged_dict){
    r_arr.push(merged_dict[key])
  }
  return r_arr
}

arr3 = merge(arr1, arr2)
console.log(arr3)

CodePudding user response：

Try this :

let arr1 = [{
    name: "Person1",
    age: 20
}, {
    name: "Person2",
    age: 30
}];
let arr2 = [{
    name: "Person1",
    email: "[email protected]"
}, {
    name: "Person3",
    age: 25
}];
function copy(source, destination) {
    for (let prop in source) {
        destination[prop] = source[prop];
    }
}
function merge(arr1, arr2) {
    let newArray = [];
    for (let i = 0, obj1; obj1 = arr1[i];   i) {
        let obj = {};
        copy(obj1, obj);
        for (let j = 0, obj2; obj2 = arr2[j];   j) {
            if (obj1.name === obj2.name) {
                copy(obj2, obj);
            }
        }
        newArray.push(obj);
    }
    for (let i = 0, obj2; obj2 = arr2[i];   i) {
        let here = false;
        for (let j = 0, obj1; obj1 = arr1[j];   j) {
            if (obj1.name === obj2.name) {
                here = true;
            }
        }
        if (!here) {
            newArray.push(obj2);
        }
    }
    return newArray;
}
let arr3 = merge(arr1, arr2);
console.log(arr3);

CodePudding user response：

  let arr1 = [
  {
   name: "Person1",
   age: 20
},
 {
 name: "Person2",
 age: 30
 }
]
 
let arr2 = [
 {
  name: "Person1",
  email: "[email protected]"
},
 {
   name: "Person3",
   age: 25
  }
] 


var arr3 = [...arr1,...arr2]