Pure JavaScript/jQuery/HTML captcha

Question

can somebody sent me a link, or to provide me an example with pure Javascript/jQuery captcha. Because I can see a lots of examples with PHP/C# ... back end. But I need just

Answer 1

I think this is not a good idea, because if validation is made in client (js), somebody can make a script to read the correct answer.

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EDIT

Anyway, if you want a useless captcha, you can play with this:

See in jsfiddle.

HTML

Pseudo-Human check.


How much is: 

Answer:

JS

$(document).ready(function() {
    var n1 = Math.round(Math.random() * 10 + 1);
    var n2 = Math.round(Math.random() * 10 + 1);
    $("#a").val(n1 + " + " + n2);
    $("#c").click(function() {
        if (eval($("#a").val()) == $("#b").val()) {
            alert("Ok! You are human!");
        } else {
            alert("error");
        }
    });
});

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EDIT 2:

My "captcha" hack:

// captcha hack
$(document).ready(function() {
     $("#b").val(eval($("#a").val()));
});

See in jsfiddle.