JavaScript : Filter an array of objects based on a condition while also filtering out unspecified keys

JavaScript fundamental (ES6 Syntax): Exercise-98 with Solution

Filter Array of Objects by Condition

Write a JavaScript program to filter an array of objects based on a condition while also filtering out unspecified keys.

• Use Array.prototype.filter() to filter the array based on the predicate fn so that it returns the objects for which the condition returned a truthy value.
• On the filtered array, use Array.prototype.map() to return the new object.
• Use Array.prototype.reduce() to filter out the keys which were not supplied as the keys argument.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2
// Define the 'reducedFilter' function to filter an array of objects and return a new array of objects containing only selected keys based on a filtering function.
const reducedFilter = (data, keys, fn) =>
  // Filter the data array based on the filtering function 'fn', then map the filtered objects to return a new array of objects containing only selected keys.
  data.filter(fn).map(el =>
    // Reduce the selected keys for each object to build a new object containing only those selected keys.
    keys.reduce((acc, key) => {
      acc[key] = el[key];
      return acc;
    }, {})
  );

// Test the 'reducedFilter' function with sample data.
const data = [
  {
    id: 1,
    name: 'john',
    age: 24
  },
  {
    id: 2,
    name: 'mike',
    age: 50
  }
];

console.log(reducedFilter(data, ['id', 'name'], item => item.age > 24)); // Output: [{ id: 2, name: 'mike' }]

Output:

[{"id":2,"name":"mike"}]

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-98-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that filters an array of objects, returning only those that meet a specified condition.
• Write a JavaScript function that iterates over an array of objects and omits properties that do not satisfy a given predicate.
• Write a JavaScript program that applies a condition to each object in an array and returns a new array with the filtered results.

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