JavaScript: Create an object composed of the properties the given function returns falsey for

JavaScript: Exercise-154 with Solution

Object from Properties Failing Function

Write a JavaScript program to create an object composed of the properties the given function returns false for. The function is invoked with two arguments: (value and key).

• Use Object.keys() and Array.prototype.filter() to remove the keys for which fn returns a truthy value.
• Use Array.prototype.reduce() to convert the filtered keys back to an object with the corresponding key-value pairs.
• The callback function is invoked with two arguments: (value, key).

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
// Define a function 'omitBy' that removes properties from an object based on a provided predicate function
const omitBy = (obj, fn) =>
  // Get the keys of the object, filter them based on the predicate function, and then reduce them back into an object
  Object.keys(obj)
    .filter(k => !fn(obj[k], k))
    .reduce((acc, key) => ((acc[key] = obj[key]), acc), {});

// Test the 'omitBy' function with an object and a predicate function
console.log(omitBy({ a: 1, b: '2', c: 3 }, x => typeof x === 'number')); // Output: { b: '2' }

Output:

{"b":"2"}

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-154-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that constructs an object containing only the key-value pairs that fail a provided predicate.
• Write a JavaScript function that filters an object’s properties based on a function that returns false, then returns the filtered object.
• Write a JavaScript program that tests each property of an object with a callback and builds a new object with properties where the callback returns false.
• Write a JavaScript program that excludes properties from an object if they pass a given truth test and returns the remaining ones.

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