How can you remove duplicates from an array of objects using reduce?

• 0
  How can you remove duplicates from an array of objects using reduce by lastname and get an array of objects without duplicates by lastname?
  
  

  const arr = [
    {
       'name': 'anna',
       'lastname': 'petrova'
    },
      {
       'name': 'vika',
       'lastname': 'ivanova'
    },
      {
       'name': 'julia',
       'lastname': 'petrova'
    },
  ]

  JavaScript Scarlett Graham, Sep 26, 2019

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3 Answers
• 0
  Like that?
  
  

  const obj = [{
  
      'name': 'anna',
  
      'lastname': 'petrova'
  
    },
  
    {
  
      'name': 'vika',
  
      'lastname': 'ivanova'
  
    },
  
    {
  
      'name': 'julia',
  
      'lastname': 'petrova'
  
    },
  
  ];
  
  
  
  const res = obj.reduce((o, i) => {
  
    if (!o.find(v => v.lastname == i.lastname)) {
  
      o.push(i);
  
    }
  
    return o;
  
  }, []);
  
  console.log(res)

  Harper Harper

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• 0

  // helers start
  
  const compose = (fn1, fn2) => x => fn1(fn2(x)); 
  
  
  
  const reduceByProp = prop => a => 
  
    a.reduce((acc, curr) => ({ ...acc, [curr[prop]]: curr }), {});
  
  
  
  const uniqByProp = prop => compose(Object.values, reduceByProp(prop));
  
  // helers end
  
  
  
  // logic start
  
  const uniqByLastname = uniqByProp('lastname')
  
  const getUniqAndPrint = compose(console.log, uniqByLastname)
  
  // logic end
  
  
  
  // exec start
  
  const arr = [
  
    {
  
       'name': 'anna',
  
       'lastname': 'petrova'
  
    },
  
      {
  
       'name': 'vika',
  
       'lastname': 'ivanova'
  
    },
  
      {
  
       'name': 'julia',
  
       'lastname': 'petrova'
  
    },
  
  ];
  
  getUniqAndPrint(arr);
  
  // exec end

  
  
  Interactive example

  Anonymous

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• 0
  solution without reduce
  
  

  const arr = [{
  
      'name': 'anna',
  
      'lastname': 'petrova'
  
  },
  
      {
  
          'name': 'vika',
  
          'lastname': 'ivanova'
  
      },
  
      {
  
          'name': 'julia',
  
          'lastname': 'petrova'
  
      },
  
  ];
  
  const table = {};
  
  const res = arr.filter(({lastname}) =>(!table[lastname] && (table[lastname] = 1)));
  
  console.log(res)

  Ezra Michael

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