I&#39;ve been browsing all over the web in search of enlightenment about continuations, and it&#39;s mind boggling how the simplest of explanations can so utterly confound a JavaScript programmer like myself. This is especially true when most articles explain continuations with code in Scheme or use monads.

Now that I finally think I&#39;ve understood the essence of continuations I wanted to know whether what I do know is actually the truth. If what I think is true is not actually true, then it&#39;s ignorance and not enlightenment.

So, here&#39;s what I know:

In almost all languages functions explicitly return values (and control) to their caller. For example:

&lt;!-- begin snippet: js console: true --&gt;

&lt;!-- language: lang-js --&gt;

    var sum = add(2, 3);

    console.log(sum);

    function add(x, y) {
        return x + y;
    }

&lt;!-- end snippet --&gt;

Now in a language with first class functions we may pass the control and return value to a callback instead of explicitly returning to the caller:

&lt;!-- begin snippet: js console: true --&gt;

&lt;!-- language: lang-js --&gt;

    add(2, 3, function (sum) {
        console.log(sum);
    });

    function add(x, y, cont) {
        cont(x + y);
    }

&lt;!-- end snippet --&gt;

Thus instead of returning a value from a function we are continuing with another function. Therefore this function is called a continuation of the first.

So what&#39;s the difference between a continuation and a callback?

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What's the difference between a continuation and a callback?