Try guessing what is the output of the following snippet:

function one() {
  function two() {
    console.log(`closure var1 - ${var1}`);
  }

  three();
  var var1 = 'var1';   
}

one();

But, if we use setTimeout(), by the time the callback closure function is executed var1 will have been initialised and its value is printed:

function one() {
 setTimeout(function() {
  console.log(`closure var1 - ${var1}`);
 }, 0);
  var var1 = 'var1';
}

one();

//output
closure var1 - var1

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