I have an array that has sequential array keys and I need to randomly select one of the keys... what's the best way to do that?
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3 Answers
Math.random() will generate a number between 0 and 1.
var key = Math.floor(Math.random() * arr.length);
1 Comment
Kelly
@DenisGorbachev's statement is incorrect. Math.random() returns 0 inclusive to 1 exclusive, meaning never 1.00. If it did, the returned index would be greater than the array length.
Have a look at JavaScript random() Method and Generating a random number in JavaScript
Comments
Only using the array length will result in never actually selecting the last item in the array, except in the extremely rare situation when the random number selected is 1.0000. Better to add .99999 to the arr.length:
var key = Math.floor(Math.random() * (arr.length + .999999))
2 Comments
Kelly
This has the potential to return a number greater than the last index.
Steven Rogers
Math.random() Gives a number somewhere from 0 to before 1 (NEVER 1). Written as [0, 1). Also, adding 0.9999999 to the array length causes a possible out of bounds error. Look at the chosen answer