JavaScript: Remove all falsy values from an object or array

JavaScript Array: Exercise-47 with Solution

Write a JavaScript program to remove all false values from an object or array.

• Use recursion.
• Initialize the iterable data, using Array.isArray(), Array.prototype.filter() and Boolean for arrays in order to avoid sparse arrays.
• Use Object.keys() and Array.prototype.reduce() to iterate over each key with an appropriate initial value.
• Use Boolean to determine the truthiness of each key's value and add it to the accumulator if it's truthy.
• Use typeof to determine if a given value is an object and call the function again to deeply compact it.

Sample Solution:

JavaScript Code :

// Source: https://bit.ly/3hEZdCl
// Function to compact an object by removing falsy values (null, false, 0, '', undefined)
const compactObject = val => {
  // Use ternary operator to filter out falsy values for arrays, otherwise use the provided value
  const data = Array.isArray(val) ? val.filter(Boolean) : val;

  // Reduce the object to a compacted version, removing falsy values recursively
  return Object.keys(data).reduce(
    (acc, key) => {
      const value = data[key];
      
      // Check if the value is truthy before including it in the result
      if (Boolean(value))
        // Recursively compact object values, if applicable
        acc[key] = typeof value === 'object' ? compactObject(value) : value;

      return acc;
    },
    // Initialize the result as an empty array for arrays, otherwise an empty object
    Array.isArray(val) ? [] : {}
  );
};

// Sample object with various values including falsy ones
const obj = {
  a: null,
  b: false,
  c: true,
  d: 0,
  e: 1,
  f: '',
  g: 'a',
  h: [null, false, '', true, 1, 'a'],
  i: { j: 0, k: false, l: 'a' }
};

// Output the result of compacting the object
console.log(compactObject(obj));

Output:

{"c":true,"e":1,"g":"a","h":[true,1,"a"],"i":{"l":"a"}}

Flowchart :

Live Demo :

See the Pen javascript-array-exercise-47 by w3resource (@w3resource) on CodePen.

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