JavaScript: Target a given value in a nested JSON object

JavaScript fundamental (ES6 Syntax): Exercise-6 with Solution

Target Value in Nested JSON

Write a JavaScript program to target a given value in a nested JSON object based on the given key.

• Use the in operator to check if target exists in obj.
• If found, return the value of obj[target].
• Otherwise use Object.values(obj) and Array.prototype.reduce() to recursively call dig on each nested object until the first matching key/value pair is found.

Sample Solution:

JavaScript Code:

// Source: https://bit.ly/2neWfJ2
// Define a function called `dig` that searches for a target key in a nested object.
const dig = (obj, target) =>
  target in obj // Check if the target key exists in the object.
    ? obj[target] // If found, return its value.
    : Object.values(obj).reduce((acc, val) => { // If not found, recursively search in nested objects.
        if (acc !== undefined) return acc; // If the target is already found, return it.
        if (typeof val === 'object') return dig(val, target); // If the current value is an object, recursively search within it.
      }, undefined); // Default return value if the target is not found.

// Test cases
const data = {
  level1: {
    level2: {
      level3: 'some data'
    }
  }
};
const dog = {
  "status": "success",
  "message": "https://images.dog.ceo/breeds/african/n02116738_1105.jpg"
};
console.log(dig(data, 'level3')); // Output: 'some data'
console.log(dig(data, 'level4')); // Output: undefined
console.log(dig(dog, 'message')); // Output: 'https://images.dog.ceo/breeds/african/n02116738_1105.jpg'

Output:

some data
undefined
https://images.dog.ceo/breeds/african/n02116738_1105.jpg

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-1-6 by w3resource (@w3resource) on CodePen.

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