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JavaScript: Create a deep clone of an object

JavaScript fundamental (ES6 Syntax): Exercise-71 with Solution

Write a JavaScript program to create a deep clone of an object.

  • Use recursion.
  • Check if the passed object is null and, if so, return null.
  • Use Object.assign() and an empty object ({}) to create a shallow clone of the original.
  • Use Object.keys() and Array.prototype.forEach() to determine which key-value pairs need to be deep cloned.
  • If the object is an Array, set the clone's length to that of the original and use Array.from(clone) to create a clone.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const deepClone = obj => {
  let clone = Object.assign({}, obj);
  Object.keys(clone).forEach(
    key => (clone[key] = typeof obj[key] === 'object' ? deepClone(obj[key]) : obj[key])
  );
  return Array.isArray(obj) ? (clone.length = obj.length) && Array.from(clone) : clone;
};
const a = { foo: 'bar', obj: { a: 1, b: 2 } };
const b = deepClone(a); // a !== b, a.obj !== b.obj
console.log(b)

Sample Output:

{"foo":"bar","obj":{"a":1,"b":2}}

Flowchart:

flowchart: Create a deep clone of an object

Live Demo:

See the Pen javascript-basic-exercise-71-1 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

Creates an object from the given key-value pairs

Example:

const tips_objectFromPairs = arr => arr.reduce((a, [key, val]) => ((a[key] = val), a), {});
console.log(tips_objectFromPairs([['x', 2], ['y', 4]])); 

Output:

[object Object] {
  x: 2,
  y: 4
}