Focus on TextBox launches PageLoad using C # .net

I have a function that sets focus to the next field through JS on the form when we press enter:

function pressEnter(obj, e) {
    var key = e.keyCode ? e.keyCode : e.which;
    if (key === 13) {
        var total = document.forms[0].elements.length;
        for (var i = 0; i < total; i++) {
            if (obj.id == document.forms[0].elements[i].id) {
                index = i + 1;
                while ((document.forms[0].elements[index].type == "hidden" || document.forms[0].elements[index].nodeName == "FIELDSET" || document.forms[0].elements[index].disabled == true)) {
                    index++;
                    if (document.forms[0].elements[index] == null)
                        return;
                }
                $('#' + document.forms[0].elements[index].id).focus();
                break;
            }
        }
    }
}

In the BODY tag, I have the following script: onkeypress = "var key = event.keyCode? Event.keyCode: e.which; return (key! = 13);" to avoid the message when [Enter]

Act normally if I set [TextBox1 autoPostBack = false] [TextBox2 autoPostBack = false]. Type TextBox1, [enter], TextBox2 receives focus and fires the body's onkeypress event.

Good.

This is where the problem arises

[TextBox1 autoPostBack = false] [TextBox2 autoPostBack = true], textBox2 , , onkeypress . TextBox2 . , TextBox AutoPostBack = true , onBlur.

, TAB, , JS.

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