Setting up the callback array and attempting to use the array index as a value in the callback

Question

When I set up the callback array this way, I get 20 in the dialog for all callbacks. I would like to get the index in an array. Is it possible? The callback function expects the callback to have one parameter. I do not control the caller because he is part of an external library. Any help is appreciated.

for (var i = 0; i < 20; i++) {
  callbackDB[i] = function(data) {
    alert(i);
  }
}

Answer 1

i , i , .

     // returns a function that closes around the `current_i` formal parameter.
var createFunction = function( current_i ) {
    return function( data ) {
        alert( current_i );
    };
};

     // In each iteration, call "createFunction", passing the current value of "i"
     // A function is returned that references the "i" value you passed in.
for (var i = 0; i < 20; i++) {
  callbackDB[i] = createFunction( i );
}

Answer 2

Object.

var callbackDB = new Array();

for (var i = 0; i < 20; i++) {
  callbackDB[i] = {
    value: i,
    callback: function() {
      alert(this.value);
    }
  };
}
			
callbackDB[5].callback();

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