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How to get Random value from an array in javascript


This example covers how to get a random number from an array of numbers in javascript.

Let’s declare an array

var array = [1,2,3,4]

Here elements index starts from zero, and the end index is an array.length-1, i.e 1

Javascript random number from array example

There are multiple ways we can do

  • use Math.random() function

Math.random()generates the random number between 0 and 1 and it is multipiled with array length and number always return between 0 to array length, This is called random Index. Math.floor() returns integer for an lower value of an floating

var array = [1,2,3,4]
let randomIndex=Math.floor(Math.random()*array.length);
var randomNumber = array[randomIndex];
console.log(randomNumber); // returns 1 or 2 or 3 or 4
  • use Lodash or underscore sample function

sample() function in lodash/underscore returns the random number for a given list of items.

syntax:

_.sample(list, [Optional Count])

List is an Array or set Optional Count- Number of Random numbers returned, Optional, Default is 1

Here is an example

var array = [1,2,3,4]
console.log(_.sample(array));   // returns 1 or 2 or 3 or 4
console.log(_.sample(array,3));   // returns array of three random numbers

Another function, sampleSize() in lodash also does the same thing.

var array = [1,2,3,4]
console.log(_.sampleSize(array));   // returns 1 or 2 or 3 or 4
console.log(_.sampleSize(array,3));   // returns array of three random numbers

Conclusion

To conclude, Learn how to get Random numbers from an array of numbers in javascript.

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