Question

So there is a page with about 50 forms.

The first form is a search, so I skip that form.

The remaining 49, I care about.

Out of those 49, I am only looking for forms with the go value equal to renew.

I wrote the code in scratch pad and it works fine.

I paste it into Greasemonkey and I get "document.forms[i].go is undefined"

Here is my code:

var i=1 ;
var total = document.forms.length -1;
while (i<=total) {

    var go_val = document.forms[i].go.value;
    if(go_val == "renew"){
        document.forms[i].setAttribute('target','_blank');
    }

    i++;
}

I have also tried this, to check if the go element exists and the form generates no errors, but does not run setattribute.

var i=0 ;
var total = document.forms.length -1;
while (i<=total) {
    if(document.forms[i].go){
    var go_val = document.forms[i].go.value;
    if(go_val == "renew"){
        document.forms[i].setAttribute('target','_blank');
    }
    }
    i++;
}

Why does it work in scratch pad, but not in Greasemonkey?

Answer 1

I have found: “Pitfall #3: Named Forms and Form Elements” and figured it out…

var i=0;
var total = document.forms.length -1;
while (i<=total) {
    var form = document.forms[i];
    if(form.elements.namedItem("go")){
        var input = form.elements.namedItem("go");
        var go_val = input.value;

        if(go_val == "renew"){
            document.forms[i].setAttribute('target','_blank');
        }
    }
    i++;
}