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JavaScript Recursion - Exercises, Practice, Solution

JavaScript Recursion [9 exercises with solution]

[An editor is available at the bottom of the page to write and execute the scripts.]

Use recursion to solve the following exercises.

1. Write a JavaScript program to calculate the factorial of a number. Go to the editor
In mathematics, the factorial of a non-negative integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example, 5! = 5 x 4 x 3 x 2 x 1 = 120
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2. Write a JavaScript program to find the greatest common divisor (gcd) of two positive numbers. Go to the editor
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3. Write a JavaScript program to get the integers in range (x, y). Go to the editor
Example : range(2, 9)
Expected Output : [3, 4, 5, 6, 7, 8]
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4. Write a JavaScript program to compute the sum of an array of integers. Go to the editor
Example : var array = [1, 2, 3, 4, 5, 6]
Expected Output : 21
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5. Write a JavaScript program to compute the exponent of a number. Go to the editor
Note : The exponent of a number says how many times the base number is used as a factor.
82 = 8 x 8 = 64. Here 8 is the base and 2 is the exponent.
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6. Write a JavaScript program to get the first n Fibonacci numbers. Go to the editor
Note : The Fibonacci Sequence is the series of numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, . . . Each subsequent number is the sum of the previous two.
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7. Write a JavaScript program to check whether a number is even or not. Go to the editor
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8. Write a JavaScript program for binary search. Go to the editor
Sample array : [0,1,2,3,4,5,6]
console.log(l.br_search(5)) will return '5'
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9. Write a merge sort program in JavaScript. Go to the editor
Sample array : [34,7,23,32,5,62]
Sample output : [5, 7, 23, 32, 34, 62]
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More to Come !

* To run the code mouse over on Result panel and click on 'RERUN' button.*

Live Demo:

See the Pen javascript-common-editor by w3resource (@w3resource) on CodePen.




JavaScript: Tips of the Day

Applies a function against an accumulator and each key in the object (from left to right)

Example:

const transform = (obj, fn, acc) => Object.keys(obj).reduce((a, k) => fn(a, obj[k], k, obj), acc);
console.log(transform(
  { a: 1, b: 2, c: 1 },
  (r, v, k) => {
    (r[v] || (r[v] = [])).push(k);
    return r;
  },
  {}
)); // { '1': ['a', 'c'], '2': ['b'] } 

Output:

[object Object] {
  1: ["a", "c"],
  2: ["b"]
}