您可以使用 Array#reduce 一次完成该操作:

You can do it using Array#reduce in one pass:

var items = [{"category":"blog","id":"586ba9f3a36b129f1336ed38","content":"foo, bar!"},{"category":"blog","id":"586ba9f3a36b129f1336ed3c","content":"hello, world!"},{"category":"music","id":"586ba9a6dfjb129f1332ldab","content":"wow, shamwow!"}];

var result = items.reduce(function(r, item) {
  var current = r.hash[item.category];
  
  if(!current) {
    current = r.hash[item.category] = { 
      category: item.category,
      items: []
    };
    
    r.arr.push(current);
  }

  current.items.push({
    id: item.id,
    content: item.content
  });
  
  return r;
}, { hash: {}, arr: [] }).arr;
  
console.log(result);

或者使用 Map 的ES6方式:

Or the ES6 way using Map:

const items = [{"category":"blog","id":"586ba9f3a36b129f1336ed38","content":"foo, bar!"},{"category":"blog","id":"586ba9f3a36b129f1336ed3c","content":"hello, world!"},{"category":"music","id":"586ba9a6dfjb129f1332ldab","content":"wow, shamwow!"}];

const result = [...items.reduce((r, { category, id, content }) => {
  r.has(category) || r.set(category, {
    category,
    items: []
  });
  
  r.get(category).items.push({ id, content });
  
  return r;
}, new Map).values()];
  
console.log(result);