将对象/数组的数据组合到 JavaScript 中的属性的最佳方法

Question

We have an array of objects with the attributes "description" and "id".

foo[0].id            // "45g-332"
foo[0].id2           // "45G-000332"
foo[0].description   // "tomatoes"
foo[1].id            // "45f-842"
foo[1].id2           // "45F-000842"
foo[1].description   // "cherries"
foo[2].id            // "45g-332"
foo[2].id2           // "45G-000332"
foo[2].description   // "peaches"

I need a variable or object in which all descriptions for the same id are combined to have a result like this:

bar[0].id            // "45g-332"
bar[0].id2           // "45G-000332"
bar[0].description   // "tomatoes; peaches"
bar[1].id            // "45f-842"
bar[1].id2           // "45F-000842"
bar[1].description   // "cherries"

… or with associative labels

bar["45g-332"].description   // "tomatoes; peaches"
bar["45f-842"].description   // "cherries"
bar["45g-332"].id2           // "45G-000332"

The only passably slim solution I came up with is (→ jsFiddle ):

let foo = [];
foo[0]  = [];
foo[1]  = [];
foo[2]  = [];

foo[0].id            = "45g-332";
foo[0].id2           = "45G-000332";
foo[0].description   = "tomatoes";
foo[1].id            = "45f-842";
foo[1].id2           = "45F-000842";
foo[1].description   = "cherries";
foo[2].id            = "45g-332";
foo[2].id2           = "45G-000332";
foo[2].description   = "peaches";

let bar = [];
for (let i in foo) {      // Loop through source (foo)
  if (bar[foo[i].id]) {    // Check if sink (bar) with id already exists
    bar[foo[i].id].description += "; " + foo[i].description;  // Add description to existing bar element
  } else {
    bar[foo[i].id] = [];   // Create new bar element
    bar[foo[i].id].description = foo[i].description;
  };
  bar[foo[i].id].id2 = foo[i].id2;  // Added by edit
};

for (let i in bar) {
  console.log("id: " + i + " has: "  + bar[i].description + " and id2: " + bar[i].id2);
};

// Result is
// "id: 45g-332 has: tomatoes; peaches and id2: 45G-000332"
// "id: 45f-842 has: cherries and id2: 45F-000842"

I'm pretty sure that there's a more plain way to do this. What's gold standard?

Answer 1

You can use reduce

 const foo = [{ id: '45g-332', id2: '45G-000332', description: 'tomatoes' }, { id: '45f-842', id2: '45F-000842', description: 'cherries' }, { id: '45g-332', id2: '45G-000332', description: 'peaches' }, { id: '45g-332', id2: '45G-000332', description: 'x' } ] const bar = foo.reduce((acc, { id, id2, description }) => { if (acc[id]) { acc[id].id2.push(id2) acc[id].description.push(description) } else { acc[id] = { id2: [id2], description: [description] } } return acc }, {}) console.log(bar)

Answer 2

For your expected result 2 here is a simple method

 const foo = [ {id: "45g-332", description: "tomatoes"}, {id: "45f-842", description: "cherries"}, {id: "45g-332", description: "peaches"} ] const bar = {} foo.forEach(d => { bar[d.id] = bar[d.id]? bar[d.id] + "; " + d. description: d.description }); console.log(bar)

For your expected result 1. you need to convert it back to an array

 const foo = [ {id: "45g-332", description: "tomatoes"}, {id: "45f-842", description: "cherries"}, {id: "45g-332", description: "peaches"} ] const bar = {} foo.forEach(d => { bar[d.id] = bar[d.id]? bar[d.id] + "; " + d. description: d.description }); const data = Object.keys(bar).map(key => ({id:key, description: bar[key]})) console.log(data)