Typescript - Craft Json object from array data

Question

This question probably will be down-voted, but just asking for my knowledge...

What I have now:

data = {COLUMN1: "DATA1", COLUMN2: "DATA2", COLUMN3: "DATA3", ..., COLUMNn: "DATAn"};

keyColumns = ["COLUMN2", "COLUMN5", "COLUMN9"];

keyValueMap = {};

What I want to get:

keyValueMap = {COLUMN2: "DATA2", COLUMN5: "DATA5", COLUMN9: "DATA9"};

What I have tried:

if (keyColumns.length > 0)
    {
      keyColumns.forEach(a => {
        keyvaluemap[a] = data[a];

      });
    };

I know that I cannot do keyvaluemap[a] = data[a], because keyvaluemap is just an object. How can I craft it so that it gets all value pairs as I wanted? The list of values in keyColumns cannot be known until runtime.

Mohammad Usman · Accepted Answer · 2018-05-17 08:55:44Z

1

You can use .reduce() method of Arrays:

let data = {COLUMN1: "DATA1", COLUMN2: "DATA2", COLUMN3: "DATA3", COLUMN4: "DATA4",COLUMN5: "DATA5", COLUMN9: "DATA9"},
    keyColumns = ["COLUMN2", "COLUMN5", "COLUMN9"];

let reducer = (obj, arr) => arr.reduce((a, c) => (a[c] = obj[c], a), {});

console.log(reducer(data, keyColumns));

answered May 17, 2018 at 8:55

Mohammad Usman

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Sergi Dote Teixidor · Accepted Answer · 2018-05-17 08:58:27Z

1

try this solution:

const result = keyColumns.reduce((acc, cur) => !!data[cur] ? ({...acc, [cur]: data[cur]}) : acc;
}, {});

answered May 17, 2018 at 8:58

Sergi Dote Teixidor

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