Check if textbox disabled or enabled in JavaScript

Question

Try using document.getElementById('textbox1').disabled

function CheckTextbox() {
  var id;
  for (var i = 1; 2 >= i; i++) {
    id = 'textbox' + i;
    console.log(id, 'is disabled ?', document.getElementById(id).disabled);
  }
}

<input type="text" id="textbox1" disabled="disabled">
<input type="text" id="textbox2">
<input type="button" onclick="CheckTextbox();" value='Check'>

function CheckTextbox() {
   var textbox = document.getElementById('textbox1');

   if (textbox.disabled) {
      // If disabled, do this 
       alert("disabled");
    } else {
       // Enter code here
        alert("Not disabled");
     }
}

<input type="text" id="textbox1" disabled="disabled">
<input type="button" onclick="CheckTextbox();">

function CheckTextbox(){

    if(document.getElementById("textbox1").disabled == true){ //here
        alert("disabled");
    }else{
        alert("enable");
    }

    if(document.getElementById("textbox2").disabled == true){ //here
        alert("disabled");
    }else{
        alert("enable");
    }

}

<script>
function CheckTextbox(){
    var textbox=document.getElementById('textbox1');

if(textbox.disabled)

   {alert("disabled"); }

else{alert("enable");}

var textbox2=document.getElementById('textbox2');
   if(textbox2.disabled){ //here
       alert("disabled");
    }else{
       alert("enable");
    }
}
</script>

<input type="text" id="textbox1" disabled="disabled">
<input type="text" id="textbox2">
<input type="button" onclick="CheckTextbox();">

<input type="text" id="textbox1" disabled="disabled">
<input type="text" id="textbox2">
<input type="button" onclick="CheckTextbox();">
<script>
 (function CheckTextbox(){
    if(document.getElementById('textbox1').disabled){
     alert("disabled");
    }else{
     alert("enable");
   }

   if(document.getElementById('textbox2').disabled){ 
    alert("disabled");
   }else{
    alert("enable");
   }
})()
</script>