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JavaScript: Get a random element from an array

JavaScript fundamental (ES6 Syntax): Exercise-149 with Solution

Write a JavaScript program to get a random element from an array.

  • Use Math.random() to generate a random number.
  • Multiply it by Array.prototype.length and round it off to the nearest whole number using Math.floor().
  • This method also works with strings.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const sample = arr => arr[Math.floor(Math.random() * arr.length)];
console.log(sample([3, 7, 9, 11]));

Sample Output:

11

Pictorial Presentation:

JavaScript Fundamental: Get a random element from an array.

Flowchart:

flowchart: Get a random element from an array

Live Demo:

See the Pen javascript-basic-exercise-149-1 by w3resource (@w3resource) on CodePen.


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JavaScript: Tips of the Day

How to remove a specific item from an array?

Find the index of the array element you want to remove using indexOf, and then remove that index with splice.

The splice() method changes the contents of an array by removing existing elements and/or adding new elements.

const array = [2, 5, 9];

console.log(array);

const index = array.indexOf(5);
if (index > -1) {
  array.splice(index, 1);
}

// array = [2, 9]
console.log(array);

The second parameter of splice is the number of elements to remove. Note that splice modifies the array in place and returns a new array containing the elements that have been removed.

For the reason of completeness, here are functions. The first function removes only a single occurrence (i.e. removing the first match of 5 from [2,5,9,1,5,8,5]), while the second function removes all occurrences:

function removeItemOnce(arr, value) {
  var index = arr.indexOf(value);
  if (index > -1) {
    arr.splice(index, 1);
  }
  return arr;
}

function removeItemAll(arr, value) {
  var i = 0;
  while (i < arr.length) {
    if (arr[i] === value) {
      arr.splice(i, 1);
    } else {
      ++i;
    }
  }
  return arr;
}
//Usage
console.log(removeItemOnce([2,5,9,1,5,8,5], 5))
console.log(removeItemAll([2,5,9,1,5,8,5], 5))

Ref: https://bit.ly/2N9nKRp