javascript - Object.keys() returns properties -

from this answer said object.keys() properties defined on object (the ones return true obj.hasownproperty(key) below code returns 4 keys , producing error confusing me.

(function () {      "use strict";      var buttons = document.getelementsbyclassname('remove');      console.log("no of keys: ", object.keys(buttons).length);      ( var in object.keys( buttons ) ) {          buttons[i].onclick = function() {              this.parentelement.remove();              console.log(this.id);          };      }  })();

<div>some entry here      <button id="0" class="remove">remove</button>  </div>  <div>another entry here      <button id="1" class="remove">remove</button>  </div>

how in javascript?

so here's how you'd loop on buttons original code using for loop:

(function () {      "use strict";      var buttons = document.getelementsbyclassname('remove');        console.log(buttons);            (var index = 0 ; index < buttons.length ; ++index) {          buttons[index].onclick = function() {              this.parentelement.remove();              console.log(this.id);          };      }  })();

<div>some entry here      <button id="a" class="remove">remove</button>  </div>  <div>another entry here      <button id="b" class="remove">remove</button>  </div>

note buttons object htmlcollection. exposes elements both index , id. in original example ids 0 , 1, quite confusing in case because causes them clash indexes. object.keys(buttons) returning ['0', '1', '0', '1'], bit odd, presumably because of number/string shenanigans. i've changed ids in example a , b object.keys(buttons) ['0', '1', 'a', 'b'].