Javascript closure?

Question

Method # 1

function transform(ar) {
    var alStr = [];
    for(var i=0; i

        

Answer 1

In Method #2 there are two problems:

1. You are returning the key name, a, rather than the array value, ar[a]. That is, rather than return a; you want return ar[a];.

2. The function will always refer to the last value looped through because it references the same scope object. To create a new scope object you will need a closure, a with block, or a bound function.

With a closure:

for(var a in ar) { 
  var O = (function(val) { 
    return function() { 
      return val; 
     }
  })(ar[a]);
  alStr.push(O); 
}

With a with block:

for(var a in ar) { 
  with({val: ar[a]}) {
    alStr.push(function() { 
      return val; 
     });
  }
} 

With a bound function:

for(var a in ar) { 
  var O = function(x) { return x; };
  alStr.push(O.bind(null, arr[a]));
}