JavaScript - Object.groupBy()

 Object.groupBy() is a powerful method in JavaScript that allows you to group elements from an iterable (such as an array) based on the values returned by a specified callback function. Let’s dive into the details:

1. What Does Object.groupBy() Do?

   • The Object.groupBy() static method groups elements of a given iterable according to the string values returned by a provided callback function.
   • The resulting object has separate properties for each group, each containing an array with the elements in that group.
   • This method is particularly useful when group names can be represented by strings.

2. Syntax:

   JavaScript

   Object.groupBy(items, callbackFn)
   

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   • items: An iterable (such as an array) whose elements will be grouped.
   • callbackFn: A function executed for each element in the iterable. It should return a value that can be coerced into a property key (string or symbol) indicating the group of the current element.
     • The function is called with the following arguments:
       • element: The current element being processed.
       • index: The index of the current element being processed.

3. Example: Grouping Food Inventory

   • Let’s say we have an array representing an inventory of different food items:
     JavaScript

     const inventory = [
       { name: "asparagus", type: "vegetables", quantity: 5 },
       { name: "bananas", type: "fruit", quantity: 0 },
       { name: "goat", type: "meat", quantity: 23 },
       { name: "cherries", type: "fruit", quantity: 5 },
       { name: "fish", type: "meat", quantity: 22 },
     ];
     

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   • We can group these elements by their type property:
     JavaScript

     const result = Object.groupBy(inventory, ({ type }) => type);
     

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   • The resulting object will look like this:
     JavaScript

     {
       vegetables: [{ name: 'asparagus', type: 'vegetables', quantity: 5 }],
       fruit: [
         { name: "bananas", type: "fruit", quantity: 0 },
         { name: "cherries", type: "fruit", quantity: 5 }
       ],
       meat: [
         { name: "goat", type: "meat", quantity: 23 },
         { name: "fish", type: "meat", quantity: 22 }
       ]
     }
     

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   • The arrow function simply returns the type of each array element each time it is called.

4. Note:

   • The elements in the returned object and the original iterable are the same (not deep copies).
   • Changing the internal structure of the elements will be reflected in both the original iterable and the returned object.

Remember, Object.groupBy() is a powerful tool for organizing data and creating meaningful groupings in your JavaScript applications! 🚀🔍📊 1: MDN Web Docs - Object.groupBy()