Echo 4 random element of array using javascript [duplicate]

You can use the below code to get a random element:

arr[Math.floor(Math.random() * arr.length)];

What about this:

var arr = ['elem1', 'elem2', 'elem3', 'elem4', 'elem5', 'elem6', 'elem7', 'elem8'];

arrLength = arr.length;

var randomNummer = Math.floor(Math.random()*arrLength);

alert(arr[randomNummer]);

jsFiddle

Use inbuilt Math.Random:

for (var i=0;i<4;i++)
{ 
  var rnd = Math.floor((Math.random()*arr.length);
  console.log(arr[rnd]);
}

If you want distinct elements, you can extract them one at a time from the array

function extractRandomElement(arr) {
  var index = Math.floor(Math.random() * arr.length);
  return arr.splice(index, 1)[0];
}

var arr = ['elem1', 'elem2', 'elem3', 'elem4', 'elem5', 'elem6', 'elem7', 'elem8'];
var arrCopy = arr.slice(0); // copy the array so the original is unchanged
var result = [];
var N = 4;

for (var i=0; i<N; i++) {
  result.push(extractRandomElement(arrCopy));
}

console.log(result);

An alternative is to shuffle (sort randomly) the array then get the first 4 elements:

var arr = ['elem1', 'elem2', 'elem3', 'elem4', 'elem5', 'elem6', 'elem7', 'elem8'];
var arrCopy = arr.slice(0); // copy the array so the original is unchanged
var N = 4;

var result = arrCopy.sort(function(){ return Math.random()-0.5; }).slice(N);

console.log(result);

This answer from a question that duplicates this one is very good: http://stackoverflow.com/a/7159251/1669279

It is an improvement over the first method above:

function extractRandomElement(arr) {
  var index = Math.floor(Math.random() * arr.length);
  var retVal = arr[index];
  arr[index] = arr.pop();
  return retVal;
}

If you are trying to get 4 unique elements of that array, you should always remove the element that you randomly retrieved:

var arr = ['elem1', 'elem2', 'elem3', 'elem4', 'elem5', 'elem6', 'elem7', 'elem8'],
    random_values = [];

for (var i = 0; i < 4; i++ ) {
    var length = arr.length,
        random = Math.floor(Math.random()*length+1);

    random_values.push(arr[random]);

    // Remove the already selected element from the arr array
    arr.splice(random, 1);
}

console.log(random_values);

You can use the below code to get a 4 random element:

var element1 = arr[Math.floor(Math.random()  * arr.length)];
var element2 = arr[Math.floor(Math.random()  * arr.length)];
var element3 = arr[Math.floor(Math.random()  * arr.length)];
var element4 = arr[Math.floor(Math.random()  * arr.length)];