如何转换JavaScript数组

Question

I have got an array:

var tab = [];

          tab.push({key: 1,value: usa});
          tab.push({key: 2,value: germany});
          tab.push({key: 1,value: india});
          tab.push({key: 1,value: russsia});
          tab.push({key: 2,value: poland});
          tab.push({key: 1,value: uk});

And what I'm trying to do is to transform above array to receive:

[{"1":"usa,india,russia,uk"},
{"2":"germany,poland"}]

I'd like to have unique values in key field, and aggregate values from value fields.

How to achive this?

Answer 1

 var tab = []; tab.push({key: 1,value: 'usa'}); tab.push({key: 2,value: 'germany'}); tab.push({key: 1,value: 'india'}); tab.push({key: 1,value: 'russsia'}); tab.push({key: 2,value: 'poland'}); tab.push({key: 1,value: 'uk'}); var transformedObject = {}; tab.forEach(function (item) { transformedObject[item.key] = transformedObject[item.key] ? `${transformedObject[item.key]}, ${item.value}` : item.value; }); console.log(transformedObject); // Access the '2' property console.log(transformedObject['2']); 

Answer 2

Using reduce :

 const orig = [{ key: 1, value: 'usa' }, { key: 1, value: 'russia' }, { key: 2, value: 'uk' }]; const result = orig.reduce((red, el) => { if (red[el.key] !== undefined) { red[el.key] += `, ${el.value}`; } else { red[el.key] = el.value; } return red; }, {}); console.log(result); 

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