Javascript - reduce the given object into one data structure

Question

I need to reduce the given object into some datastructure. This is my input object.

const receiver =  {
      USER1: {
        module: ['a_critical', 'a_normal','b_normal']
      },
      USER2: {
        module: ['a_critical', 'a_normal','b_critical']
      }, 
      USER3: {
        module: ['a_critical']
      }
    };

const allModules = ['a_normal', 'a_critical', 'b_normal', 'b_critical']; 

Desired output:

{
  "a_critical": [
    {
      "user": [
        "USER1", "USER2", "USER3"
      ]
    }
  ],
  "a_normal": [
    {
      "user": [
        "USER1", "USER2"
      ]
    }
 ],
  "b_normal": [
    {
      "user": [
        "USER1"
      ]
    }
  ],
  "b_critical": [
    {
      "user": [
        "USER2"
      ]
    }
  ]
} 

I have tried doing but i was getting some problems. I am getting some duplicate properties which should be there. I can share the code on what i have tried.

const receiverObj = {};

let count = 0;
Object.keys(receiver).forEach((item) => {
    receiver[item].module.forEach((module) => {
      if(allModules.includes(module)) {
        count  = 1;
        if(count) {
        receiverObj[module] = [];
           receiverObj[module].push({user: [item] });
        }
        receiverObj[module].push({user: item });
        count = 0;
      }
    })
});

console.log(JSON.stringify(receiverObj, null, 2)); 

Actual result which i got:

{
  "a_critical": [
    {
      "user": [
        "USER3"
      ]
    },
    {
      "user": "USER3"
    }
  ],
  "a_normal": [
    {
      "user": [
        "USER2"
      ]
    },
    {
      "user": "USER2"
    }
  ],
  "b_normal": [
    {
      "user": [
        "USER1"
      ]
    },
    {
      "user": "USER1"
    }
  ],
  "b_critical": [
    {
      "user": [
        "USER2"
      ]
    },
    {
      "user": "USER2"
    }
  ]
} 

Is there any optimal way of doing this ? can someone help ?

Answer 1

Iterate over each module in a reduce callback, creating a { user: [] } object in the accumulator if it doesn't exist yet, and then push to that array:

const receiver =  {
      USER1: {
        module: ['a_critical', 'a_normal','b_normal']
      },
      USER2: {
        module: ['a_critical', 'a_normal','b_critical']
      }, 
      USER3: {
        module: ['a_critical']
      }
    };

const output = Object.entries(receiver)
  .reduce((a, [user, { module }]) => {
    module.forEach((name) => {
      if (!a[name]) {
        a[name] = { user: [] };
      }
      a[name].user.push(user);
    });
    return a;
  }, {});
console.log(output);

You could also create the accumulator object in advance, if you wanted, since you have allModules, thereby avoiding conditionals inside the .reduce:

const receiver =  {
      USER1: {
        module: ['a_critical', 'a_normal','b_normal']
      },
      USER2: {
        module: ['a_critical', 'a_normal','b_critical']
      }, 
      USER3: {
        module: ['a_critical']
      }
    };

const allModules = ['a_normal', 'a_critical', 'b_normal', 'b_critical']; 
const accum = Object.fromEntries(
  allModules.map(
    name => [name, { user: [] }]
  )
);

const output = Object.entries(receiver)
  .reduce((a, [user, { module }]) => {
    module.forEach((name) => {
      a[name].user.push(user);
    });
    return a;
  }, accum);
console.log(output);