AVI

var num = 5,
    arr = [1, 5, 7, 9];
   
all=arr.filter(function(item){ return item !=num; }).length?false:true;

var num = 5,
    arr = [1, 5, 7, 9],
    all = arr.length?true:false;

for(var i = 0; i < arr.length; i++) 
    if(arr[i] != num) {
        all = false;
        break;
    }