Question 51744 in Javascript Question posted in
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Merge 2 array of objects with different properties – Javascript

I have 2 arrays of objects:

array1 = [{"id":1,"cost":200,"qty":56},{"id":2,"cost":100,"qty":16}];
array2 = [{"id":1,"cost":200,"desc":"a good one"},{"id":2,"cost":100,"desc":"a bad one"},{"id":3,"cost":50,"desc":"an okay one"}];

I want to merge them so it looks like this:

[{"id":1,"cost":200,"qty":56,"desc":"a good one"},{"id":2,"cost":100,"qty":16,"desc":"a bad one"}];

Please notice the new array has properties from both arrays but it left out the object that was not present in the first one.

I tried this:

var mergethem = function() {
     var array1 = [{"id":1,"cost":200,"qty":56},{"id":2,"cost":100,"qty":16}];
     var array2 = [{"id":1,"cost":200,"desc":"a good one"},{"id":2,"cost":100,"desc":"a bad one"},{"id":3,"cost":50,"desc":"an okay one"}];
    
     var newarray= array2.filter(i => array1.map(a=> { if(a.id == i.id) i.qty = a.qty; return i; }));
     
     return newarray.filter(i=> { if(i.qty) return i; });
    }
    
    console.log(mergethem());

this seems to work sometimes and some times it doesn’t depending on the environment. I can’t pinpoint what the problem is so I would like to ask for alternatives to try out.

Tags:

2

Answers


  1. 0

    You could get references of the objects of the second array and map the first while adding properties of the second array, if exist.

    const
    array1 = [{ id: 1, cost: 200, qty: 56 }, { id: 2, cost: 100, qty: 16 }],
    array2 = [{ id: 1, cost: 200, desc: "a good one" }, { id: 2, cost: 100, desc: "a bad one" }, { id: 3, cost: 50, desc: "an okay one" }],
    references2 = Object.fromEntries(array2.map(o => [o.id, o])),
    result = array1.map(o => ({ ...o, ...references2[o.id] }));

console.log(result);
    .as-console-wrapper { max-height: 100% !important; top: 0; }
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  2. 0 
    const array1 = [
  {"id":1,"cost":200,"qty":56},
  {"id":2,"cost":100,"qty":16}
];

const array2 = [
  {"id":1,"cost":200,"desc":"a good one"},
  {"id":2,"cost":100,"desc":"a bad one"},
  {"id":3,"cost":50,"desc":"an okay one"}
];

const result = array1.reduce((previousValue, currentValue) => {
  const needObj = array2.find(o => o.id === currentValue.id) ?? {};
  previousValue.push({...currentValue, ...needObj});
  return previousValue;
}, []);

console.log(result);
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