Passing parameters to a form, via JavaScript -

i have form passes number of parameters. far, stock parameters being passed:

var params = "title=" + document.getelementbyid("title").value +               "&url=" + document.getelementbyid("url").value +               "&snippet=" + document.getelementbyid("snippet").value +              "&tags=" + document.getelementbyid("tags").value +              "&status_bookmark=" + document.getelementbyid("status_bookmark").value +              "&comment=" + document.getelementbyid("comment").value +              "&status_comment=" + document.getelementbyid("status_comment").value; 

i'm attempting append additional form elements parameter string, are:

var i, lng = document.getelementbyid('addbookmark').length; // if length property undefined, there 1 checkbox. if (typeof lng === "undefined") {     params + "&topic-link-item-1=" + document.getelementbyid("topic-link-item-1").value;     params + "&topic-link-comment-box-1=" + document.getelementbyid("topic-link-comment-box-1").value; } else {     (i = 0; < lng; i++) {         params + "&topic-link-item-" + + "=" + document.getelementbyid("topic-link-item-" + i).value;         params + "&topic-link-comment-box-" + + "=" + document.getelementbyid("topic-link-comment-box-" + i).value;     } } 

here, i've used code taken another stackoverflow article, , can see, i'm trying build series of paired parameters match ad hoc form elements i'm generating elsewhere via jquery, works.

however, these values appear not getting passed via form, while other form elements being passed.

any suggestions?

update

i've revised code, per suggestions, it's not working:

var i, formobj = document.form['addbookmark'], formobjlng = document.form['addbookmark'].length; // if length property undefined, there 1 checkbox. if ((typeof formobjlng !== "undefined")) {     (i = 0; < formobjlng; i++) {         if ((formobj.elements['topic-link-item-' + i].type == "checkbox") && (formobj.elements['topic-link-item-' + i].checked)) {             params = params + "&topic-link-item-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-item-" + i)).value;             params = params + "&topic-link-comment-box-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-comment-box-" + i)).value;         }     } } 

as form, it's form id of "addbookmark", , again state said earlier, else works exception of im attempting here.

there 2 issues code. need url encode values using encodeuricomponent function. need assign result params variable when concatenating:

var params =      "title=" + encodeuricomponent(document.getelementbyid("title").value) +      "&url=" + encodeuricomponent(document.getelementbyid("url").value) +      "&snippet=" + encodeuricomponent(document.getelementbyid("snippet").value) +     "&tags=" + encodeuricomponent(document.getelementbyid("tags").value) +     "&status_bookmark=" + encodeuricomponent(document.getelementbyid("status_bookmark").value) +     "&comment=" + encodeuricomponent(document.getelementbyid("comment").value) +     "&status_comment=" + encodeuricomponent(document.getelementbyid("status_comment").value); 

and other values adding:

var i, lng = document.getelementbyid('addbookmark').length; // if length property undefined, there 1 checkbox. if (typeof lng === "undefined") {     params += "&topic-link-item-1=" + encodeuricomponent(document.getelementbyid("topic-link-item-1").value);     params += "&topic-link-comment-box-1=" + encodeuricomponent(document.getelementbyid("topic-link-comment-box-1").value); } else {     (i = 0; < lng; i++) {         params += "&topic-link-item-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-item-" + i).value);         params += "&topic-link-comment-box-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-comment-box-" + i).value);     } } 

notice how:

params += "&topic-link-item-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-item-" + i).value); 

which equivalent to:

params = params + "&topic-link-item-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-item-" + i).value); 

is not same doing initially:

params + "&topic-link-item-" + + "=" + encodeuricomponent(document.getelementbyid("topic-link-item-" + i).value); 

you concatenating 2 values , never assigning result params variable.