JavaScript convert Array of Array of Objects into Array of objects

Question

I need convert Array of Array of Objects into a simple Array of objects using JavaScript

Below i go put the current code with the current output

const result = [
  [
    {
      name: '1'
    },
    {
      name: '2'
    }
  ],
  [
    {
      name: '3'
    },
    {
      name: '4'
    }
  ],
  [
    {
      name: '5'
    }
  ],
  [
    {
      name: '6'
    }
  ]
]

const a = result.map(item => {
  return Object.assign({}, ...item)
})


console.log(a)

Output of the above code (current and wrong output)

[ { "name": "2" }, { "name": "4" }, { "name": "5" }, { "name": "6" } ]

The expected and needed output

[
  {
    name: '1'
  },
  {
    name: '2'
  },
  {
    name: '3'
  },
  {
    name: '4'
  },
  {
    name: '5'
  },
  {
    name: '6'
  }
]

junvar · Accepted Answer · 2019-06-06 21:21:32Z

4

Looks like you're looking for flat (mdn)

const result = [
  [
    {
      name: '1'
    },
    {
      name: '2'
    }
  ],
  [
    {
      name: '3'
    },
    {
      name: '4'
    }
  ],
  [
    {
      name: '5'
    }
  ],
  [
    {
      name: '6'
    }
  ]
]

const a = result.flat();


console.log(a)

answered Jun 6, 2019 at 21:21

junvar

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Comments

Jack Bashford · Accepted Answer · 2019-06-06 21:38:11Z

1

There's a simple and well-supported way to flatten arrays without using flat - use reduce and push (not concat for efficiency).

const result = [
  [
    {
      name: '1'
    },
    {
      name: '2'
    }
  ],
  [
    {
      name: '3'
    },
    {
      name: '4'
    }
  ],
  [
    {
      name: '5'
    }
  ],
  [
    {
      name: '6'
    }
  ]
]

const a = result.reduce((acc, curr) => (acc.push(...curr), acc));

console.log(a);

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

ES5 syntax:

var result = [
  [
    {
      name: '1'
    },
    {
      name: '2'
    }
  ],
  [
    {
      name: '3'
    },
    {
      name: '4'
    }
  ],
  [
    {
      name: '5'
    }
  ],
  [
    {
      name: '6'
    }
  ]
]

var a = result.reduce(function(acc, curr) {
  return (Array.prototype.push.apply(acc, curr), acc);
});

console.log(a);

edited Jun 6, 2019 at 21:38

answered Jun 6, 2019 at 21:25

Jack Bashford

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3 Comments

slider Over a year ago

This is inefficient as concat would create a new array every time. A more efficient version would be to push elements to acc.

Jack Bashford Over a year ago

OK @slider I'll change that.

Jack Bashford Over a year ago

Fixed @slider, any better?

basic · Accepted Answer · 2019-06-06 21:23:52Z

0

You could use Array.prototype.concat to merge the arrays.

Array.concat

const result = [
  [
    {
      name: '1'
    },
    {
      name: '2'
    }
  ],
  [
    {
      name: '3'
    },
    {
      name: '4'
    }
  ],
  [
    {
      name: '5'
    }
  ],
  [
    {
      name: '6'
    }
  ]
]

const b = Array.prototype.concat.apply([], result);
console.log(b);

answered Jun 6, 2019 at 21:23

basic

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