Question

Inside a function I need to test if another variable function exists and then call it if it does.

function div1_load(){
  // do something
}

function main(id){
  var func = id + '_load';
  if (func is function) {
    func.call();
  }
}
main('div1');

I can think of two ways to test, but both involve eval() which I would like to avoid.

1. typeof eval(func) === ‘function’
2. eval(‘typeof(‘ + func + ‘)’) === ‘function’

Is there a way without using eval() ?
If not, which of my two methods is most secure ?

Answer 1

function main(id, ns) {
    if (!ns) {
        ns = window;
    }
    if (typeof ns[id + '_load'] === "function") {
        ns[id + '_load']();
    }
}

function div1_load() {
    alert("div1_load() was called");
}

main('div1');

var test = {
    div1_load: function() {
        alert("test.div1_load() was called");
    }
};

main('div1', test);​