Variable contains in the array? JavaScript

how to check that the variable occurs in an array?

In Example

var X = 5;
var newArray = [1,2,5]

And now something like this

if(X.isin(newArray)
{ document.write( "YES");}

something like this exist? :P

Solution

if (newArray.indexOf(X) > -1) {
    // value X exists in newArray
}