javascript - How to call function using the value stored in a variable? -

i have variable

var functionname="givevote"; 

what need is, want call function stored in var functionname. tried using functionname(); . not working. please help.

edit based on same problem, have

$(this).rules("add", {txtinf: "^[a-za-z'.\s]{1,40}$" });  

rules predifined function takes methodname:, here have hardcoded txtinf. want supply javascript variable here, make code generic. var methodname="txtinf";

here want evaluate methodname first before being used in rules function.

$(this).rules("add", {mehtodname: "^[a-za-z'.\s]{1,40}$" });  

you have handful of options - 2 basic ones include window[functionname]() or settimeout(functionname, 0). give shot.

edit: if variable string name of function, use those; otherwise, if you're able assign function reference variable (eg, var foo = function() {};), use foo() notation, or foo.apply(this, []), etc.

edit 2: evaluate methodname in place prior $(this).rules() firing, you'd apply first syntax above (using window object), so:

$(this).rules("add", {window[methodname](): ...}); 

i think that's you're asking - if not, please clarify bit more , i'll happy rewrite solution.