Trigger button click with JavaScript on Enter key in Text Box

<input type="text" id="txtSearch" />
<input type="button" id="btnSearch" value="Search" onclick="doSomething();" />

$("#id_of_textbox").keyup(function(event){
  if(event.keyCode == 13){
    $("#id_of_button").click();
  }
});

<input type="text" id="txtSearch" onkeydown="if (event.keyCode == 13) document.getElementById('btnSearch').click()"/>
<input type="button" id="btnSearch" value="Search" onclick="doSomething();" />

<input type="text" id="txtSearch" onkeypress="searchKeyPress(event);" />
	<input type="button" id="btnSearch" Value="Search" onclick="doSomething();" />

	<script>
	function searchKeyPress(e)
	{
		// look for window.event in case event isn't passed in
		if (window.event) { e = window.event; }
		if (e.keyCode == 13)
		{
			document.getElementById('btnSearch').click();
		}
	}
	</script>

if (document.layers)
    document.captureEvents(Event.KEYDOWN);
document.onkeydown =
    function (evt) {
        var keyCode = evt ? (evt.which ? evt.which : evt.keyCode) : event.keyCode;
        if (keyCode == 13) {
            //For enter.
            //Your function here.
        }
        if (keyCode == 27) {
            //For escape.
            //Your function here.
        }
        else
            return true;
    };

<input type="submit" id="btnSearch" value="Search" onclick="return doSomething();" />

onkeydown="javascript:if (event.which || event.keyCode){if ((event.which == 13) || (event.keyCode == 13)) {document.getElementById('btnSearch').click();}};"

<input type="text" id="txtSearch" onchange="doSomething();" />
<input type="button" id="btnSearch" value="Search" onclick="doSomething();" />

event.returnValue = false

$(document).keypress(function(event){
    var keycode = (event.keyCode ? event.keyCode : event.which);
    if(keycode == '13'){
        $('#btnSearch').click();
}

<script type="text/javascript">
function blank(a) { if(a.value == a.defaultValue) a.value = ""; }

function unblank(a) { if(a.value == "") a.value = a.defaultValue; }
</script>
<input type="text" value="email goes here" onfocus="blank(this)" onblur="unblank(this)" />