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[jQuery] isメソッドで:invalidを使えるようにする

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久しぶりにjQuery触っていたら、isメソッドに:invalid擬似クラスを指定したところでSyntax Errorになった。
自家製CSS Selectorだし、いずれ先のバージョンで対応されるんだろうけど、取り急ぎ使えないと不便だったのでjQueryオブジェクトを拡張。

$.extend($.expr[':'], {
  invalid: function(e, inx, match){
    var invalids = document.querySelectorAll(':invalid');
    var result = false;
    for(var i=0; i<invalids.length; i++){
      if(e === invalids[i]){
        result = true;
    return result;


  alert('Validation Error!');
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