const groupBy = <T extends Object>(data: T[], key: keyof T): Record<string, T[]> => {
  return data.reduce((acc: Record<string, T[]>, cur: T) => {
    var group = cur[key] as unknown as string;
 
    if (acc[group] === undefined) {
      acc[group] = [];
    }
 
    acc[group].push(cur);
    return acc;
  }, {});
};

const groupBy = <T extends Object>(data: T[], key: keyof T): Record<string, T[]> => {
  return data.reduce((acc: Record<string, T[]>, cur: T) => {
    var group = cur[key] as unknown as string;
 
    if (acc[group] === undefined) {
      acc[group] = [];
    }
 
    acc[group].push(cur);
    return acc;
  }, {});
};

interface Snippet {
  title: string;
  category: string;
}
 
const allSnippets: Snippet[] = [
  { title: "snippet1", category: "React" },
  { title: "snippet2", category: "JavaScript" },
  { title: "snippet3", category: "TypeScript" },
  { title: "snippet4", category: "React" },
  { title: "snippet5", category: "React" },
  { title: "snippet6", category: "JavaScript" },
  { title: "snippet7", category: "TroubleShooting" },
];
 
console.log(groupBy(allSnippets, "category"));

interface Snippet {
  title: string;
  category: string;
}
 
const allSnippets: Snippet[] = [
  { title: "snippet1", category: "React" },
  { title: "snippet2", category: "JavaScript" },
  { title: "snippet3", category: "TypeScript" },
  { title: "snippet4", category: "React" },
  { title: "snippet5", category: "React" },
  { title: "snippet6", category: "JavaScript" },
  { title: "snippet7", category: "TroubleShooting" },
];
 
console.log(groupBy(allSnippets, "category"));

{
  "JavaScript": [
    { "title": "snippet2", "category": "JavaScript" },
    { "title": "snippet6", "category": "JavaScript" }
  ],
  "React": [
    { "title": "snippet1", "category": "React" },
    { "title": "snippet4", "category": "React" },
    { "title": "snippet5", "category": "React" }
  ],
  "TroubleShooting": [{ "title": "snippet7", "category": "TroubleShooting" }],
  "TypeScript": [{ "title": "snippet3", "category": "TypeScript" }]
}

{
  "JavaScript": [
    { "title": "snippet2", "category": "JavaScript" },
    { "title": "snippet6", "category": "JavaScript" }
  ],
  "React": [
    { "title": "snippet1", "category": "React" },
    { "title": "snippet4", "category": "React" },
    { "title": "snippet5", "category": "React" }
  ],
  "TroubleShooting": [{ "title": "snippet7", "category": "TroubleShooting" }],
  "TypeScript": [{ "title": "snippet3", "category": "TypeScript" }]
}