Let me see if I understand: you want to call a function (preload loaded!) whose name you have in the form of a string, right?

Just use the window object!

Let's use the foo function as an example:

function foo() {
    alert('foo!');
}

The foo function is a property of the window object. That is, there are three ways to call this function:

• Only foo() .
• More completely: window.foo() .
• Or: window['foo']() .

Notice that in the third example we use a string with the name of the method ( foo ). Remember that, roughly speaking, a JavaScript object is just a "big hashmap".

The third example would suit you!

Why eval did not work?

Following the example above,% wont work. I can not tell you why in your case it did not work ...

Of course, I will not go into the discussion of not using the eval('foo()') function because you have already demonstrated a little understanding about it (:

p.s .: consider doing otherwise

Using the name of a reference to be called programmatically can mean a difficult maintenance and / or confusing code (especially if the code grows).

Remember that in JavaScript functions are first-class citizens . That is, functions can be returned and assigned to variables:

function obterAcao() {
    return function() { alert('ação!'); }
}

var acao = obterAcao();
//...
acao();

Perhaps using functions in this way will make your code more readable and maintainable. This is the tip.

You're doing it right. Only missing this:

script.setAttribute('type','text/javascript'); 

to tell the Browser what kind of content it is.

Take a look at this example and notice that the alert pops up twice. One when it loads, and another one after 5 seconds, because the newly inserted function is now present / in the scope of the code.

function funcao_um(parametro) {
    var script = document.createElement('script');
    script.setAttribute('type','text/javascript'); 
    script.src = 'https://rawgit.com/SergioCrisostomo/version-files/master/soPT_script1.js';
    document.getElementsByTagName('head')[0].appendChild(script);
}
funcao_um();
setTimeout(function(){
  dentroDoScript();
}, 5000)

And inside the external file I have this:

function dentroDoScript(){
     alert('Estou vivo!');
}
dentroDoScript();

To include a script dynamically, use the following function:

function include(url, callback, conteudo) {
    var script = document.createElement('script');

    script.type = 'text/javascript';
    script.async = 'async';
    script.defer = 'defer';
    script.src = url;
    if (conteudo) script.innerText = conteudo;

    if (script.readyState) {
        script.onreadystatechange = function () {
            if (script.readyState === 'loaded' || script.readyState === 'complete') {
                script.onreadystatechange = null;
                callback && callback();
            }
        }
    }
    else {
        script.onload = callback;
    }

    document.body.appendChild(script);
}

And use it like this:

include('/meuscript.js', function() {
    // código aqui
});

Another example, loading jQuery dynamically:

include('http://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.js', function() {
    alert($('body').html());
}); 

If the second function is in global scope, just invoke it from the window object. Also remember to wait for the script to load as indicated in the other responses:

function funcao_um (parametro) {
    var script = document.createElement('script');
    script.src = 'nomeDoArquivo.js';
    document.getElementsByTagName('head')[0].appendChild(script);
    script.onload = function() {
        // invoca a função do segundo arquivo
        window["funcao_" + parametro]();
    }
}