Getting a Random Value from a JavaScript Array

Getting a random value from a JavaScript array

It's a simple one-liner:

const randomElement = array[Math.floor(Math.random() * array.length)];

For example:

const months = ["January", "February", "March", "April", "May", "June", "July"];

const random = Math.floor(Math.random() * months.length);
console.log(random, months[random]);

Get a random item from a JavaScript array

var item = items[Math.floor(Math.random()*items.length)];

pick a random item from a javascript array

Use Math.random * the length of the array, rounded down, as an index into the array.

Like this:

var answers = [

  "Hey",

  "Howdy",

  "Hello There",

  "Wotcha",

  "Alright gov'nor"

]

var randomAnswer = answers[Math.floor(Math.random() * answers.length)];

console.log(randomAnswer);

Create an array with random values

Here's a solution that shuffles a list of unique numbers (no repeats, ever).

for (var a=[],i=0;i<40;++i) a[i]=i;

// http://stackoverflow.com/questions/962802#962890
function shuffle(array) {
  var tmp, current, top = array.length;
  if(top) while(--top) {
    current = Math.floor(Math.random() * (top + 1));
    tmp = array[current];
    array[current] = array[top];
    array[top] = tmp;
  }
  return array;
}

a = shuffle(a);

If you want to allow repeated values (which is not what the OP wanted) then look elsewhere. :)

How to get a number of random elements from an array?

Try this non-destructive (and fast) function:

function getRandom(arr, n) {
    var result = new Array(n),
        len = arr.length,
        taken = new Array(len);
    if (n > len)
        throw new RangeError("getRandom: more elements taken than available");
    while (n--) {
        var x = Math.floor(Math.random() * len);
        result[n] = arr[x in taken ? taken[x] : x];
        taken[x] = --len in taken ? taken[len] : len;
    }
    return result;
}

Generate new random values and store in an array

Per sam's question in the comments, here's the code:

function shuffle(array) {
    for (var i = array.length - 1; i > 0; i--) {
        var j = Math.floor(Math.random() * (i + 1));
        var temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}

pairs = [];

for (let i = 0; i <= 3; i++) {
    for (let j = 0; j <= 3; j++) {
        pairs.push([i, j]);
    }
}

shuffle(pairs);

pairs = pairs.slice(0, 10);

console.log(pairs);

How to retrieve a random value from an array that has values separate by a new line

What you want is to get the text from each <option>

def grabValues = scriptAll('#CarId option', '_.textContent')

This will give you an array of text values like

["Mercedes","BMW","Lexus","Honda","Toyota","VW"]

To get a random index you would use

Math.floor(Math.random() * grabValues.length)

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