Some interesting phenomena in JS

1,js about function promotion (in ES5)

function f () {Console.log (' I am outside! ' )}    (function() {        if(false) {//             The function f () {Console.log ("I am inside!") that declares a function in the  if, loop code block is certainly not allowed in strict mode.             )}        }}        (f ();    }) ();     // The result is I am inside!      Because there is a variable function promotion in ES5,  repeated declarations, followed by overwriting the front, so the final function is functions f () {Console.log ("I am inside!")}

Using a let declaration in ES6 produces a block-level scope without immediately executing an anonymous function.

2.

alert (a) a (); var a=3; function A () {    alert (ten)}   alert (a) a=6; a ();   ------------Split Line------------------alert (a) a (); var a=3; var a=function() {    alert (ten)}   alert (a) a=6; a (); Link: https://juejin.im/post/5a0c170c6fb9a0451c39eff2

Some interesting phenomena in JS