javascript - Why does window.onload allow me to use functions when they are used as function expressions? -

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• var functionname = function() {} vs function functionname() {} 28 answers

i understand function expressions must expressed @ top if want use them vs function declarations hoisted top.

when call constructor window.onload, works. if don't have window.onload, , call constructor before function expression, code breaks.

<script type="text/javascript">          window.onload = function () {             var c = new c();         }  // works, if delete window.onload code breaks.          var c = function () {             console.log("test");          };   </script> 

that's simple. window.onload executed later, when c defined, if call new c throw because c undefined.

move call after definition, or define using 'function' keyword, not 'var'