var funcName = function() {} vs function funcName() {}

2 ways of declaring functions in js:

var functionOne = function() {
    // code
};
function functionTwo() {
    // code
}

The difference is that functionOne is defined at run-time, whereas functionTwo is defined at parse-time for a script block. For example:

<script>
  // Error
  functionOne();
 
  var functionOne = function() {
  }
</script>
 
<script>
  // No error
  functionTwo();
 
  function functionTwo() {
  }
</script>

In JavaScript, declarations are hoisted. Meaning that var a = 1; var b = 2; becomes var a; var b; a = 1; b = 2.

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