Create send params demo

JavaScript

var userId = "123123123";
var friendIds = ["123456789", "234567891", "345678912"];

function createParams(userId, friendIds) {
    var output = "user_id=" + userId;
    
    for(var i = 0, max = friendIds.length; i < max; i++) {
        output += "&friend_ids[" + i + "]=" + friendIds[i];
    }
    
    return output;
}

alert( createParams(userId, friendIds) );