var x = function (){};

var x = function y(){};
console.log(y)//報錯y未定義

function x() {};
 
var x = function (){};

x =new Function (){};

x = (x,y) => {x+y}

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function f1(){};
f1.name;// f1

var f2 = function(){};
f2.name; //f2

var f3 = function f4(){};
f3.name; //f4

f5 = new Function (){};
f5.name; //anonymous