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function clsAlphaNoOnly (e) { // Accept only alpha numerics, no special characters
var regex = new RegExp("^[a-zA-Z0-9 ]+$");
var str = String.fromCharCode(!e.charCode ? e.which : e.charCode);
if (regex.test(str)) {
return true;
}
e.preventDefault();
return false;
}
<input type="text" id="input" onkeypress="clsAlphaNoOnly(event)" onpaste="return false;">