Everyone,need a help! Look at the code below.Can you guys explain that why the function "sayhi" is not defined?thanks

Question

let phrase = "Hello";
if (true) {
let user = "John";
function sayHi() {
alert(`${phrase}, ${user}`);
}
}
sayHi();

Answer 1

ES5 forbids declaring functions inside blocks, so the code doesn't work in strict mode (see attachment)

In nonstrict mode something strange happens - the function is not hoisted to the top like it was pre ES5, so it gets access to the block scope user variable. Also making the if condition false skips definition of the function, resulting in an error.

So nonstrict mode (at least on sololearn) neither informs you of an error, nor preserves backwards compatibility

https://code.sololearn.com/W3DBKY84Wzl5/?ref=app

Answer 2

Volodymyr Chelnokov thanks! Now I know this is the problem of strict mode

Answer 3

may can be friends with u?