Add element to array conditionally

Question

I have two array

var arr1 = ["xxx", "yyy"]

var arr2 = [
 {domain="xxx", kwd="a", position=1},
 {domain="yyy", kwd="a", position=2},

 {domain="xxx", kwd="b", position=1},
 {domain="yyy", kwd="b", position=2},

 {domain="yyy", kwd="c", position=2},

 {domain="xxx", kwd="d", position=1}

 ]

I want that when for a domain in arr1 there isn't a kdw in arr2 for that domain, will be push position="n/a". So based of the arrays above the output should be:

var arr3 = [
 {domain="xxx", kwd="a", position=1},
 {domain="yyy", kwd="a", position=2},

 {domain="xxx", kwd="b", position=1},
 {domain="yyy", kwd="b", position=2},

 {domain="xxx", kwd="c", position="n/a"},
 {domain="yyy", kwd="c", position=2},

 {domain="xxx", kwd="d", position=1},
 {domain="yyy", kwd="d", position="n/a"},
    
]

I have no idea on how to achieve that. I have started this piece of code but I don't know if it is relevant or not:

var arr1 = [domain="xxx", domain="yyy" ]
        
var arr2 = [{domain="xxx", kwd="a", position=1},{domain="yyy", kwd="a", position=2}, {domain="xxx", kwd="b", position=1}, {domain="yyy", kwd="b", position=2},{domain="yyy", kwd="c", position=2}, {domain="xxx", kwd="d", position=1}]   
    
    var arr3 [];
        
        var i;
        for (i = 0; i < arr2.domain.length; i++) { 
        if(// logic  ) {
            arr3.push({
            domain: arr2[i].domain,
            kwd: arr2[i].kwd,
            position: arr2[i].position
          }) else {
            arr3.push({
            domain: arr2[i].domain,
            kwd: arr2[i].domain,
            position: "n/a"
          }
        }
   }

}

Thanks in advance for any help. Kind regards.

one question, how doesn't arr2 and arr3 produce an error? — The Bomb Squad
– The Bomb Squad, Commented May 6, 2021 at 23:28
Then provide samples with unique values and expected results. Hard to figure it out when you made them all the same. See minimal reproducible example — charlietfl
– charlietfl, Commented May 7, 2021 at 2:30

Andy Ray · Accepted Answer · 2021-05-07 03:06:21Z

1

var arr1 = ["xxx", "yyy"];

var arr2 = [
  { domain: "xxx", kwd: "a", position: 1 },
  { domain: "yyy", kwd: "a", position: 2 },

  { domain: "xxx", kwd: "b", position: 1 },
  { domain: "yyy", kwd: "b", position: 2 },

  { domain: "yyy", kwd: "c", position: 2 },

  { domain: "xxx", kwd: "d", position: 1 }
];

const grouped = arr2.reduce((group, entry) => {
  const lookup = group[entry.kwd] || {};
  return {
    ...group,
    [entry.kwd]: {
      ...lookup,
      [entry.domain]: entry
    }
  };
}, {});

const filledIn = Object.entries(grouped).reduce(
  (arr, [key, group]) => [
    ...arr,
    ...arr1.map((domain) =>
      domain in group
        ? group[domain]
        : {
            domain,
            kwd: key,
            position: "n/a"
          }
    )
  ],
  []
);

console.log(filledIn);

answered May 7, 2021 at 3:06

Andy Ray

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1 Comment

user14484722 Over a year ago

Thanks for your help. I tried to edit a bit your script but I got an issue. If you please could have a look stackoverflow.

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