javascript - Why use named function expressions?

Question

We have two different way for doing function expression in JavaScript:

Named function expression (NFE):

var boo = function boo () {
  alert(1);
};

Anonymous function expression:

var boo = function () {
  alert(1);
};

And both of them can be called with boo();. I really can't see why/when I should use anonymous functions and when I should use Named Function Expressions. What difference is there between them?

question from:https://stackoverflow.com/questions/65830411/difference-between-req-param-function-and-req-param-function-param

Answer 1

In the case of the anonymous function expression, the function is anonymous — literally, it has no name. The variable you're assigning it to has a name, but the function does not. (Update: That was true through ES5. As of ES2015 [aka ES6], often a function created with an anonymous expression gets a true name [but not an automatic identifier], read on...)

Names are useful. Names can be seen in stack traces, call stacks, lists of breakpoints, etc. Names are a Good Thing?.

(You used to have to beware of named function expressions in older versions of IE [IE8 and below], because they mistakenly created two completely separate function objects at two completely different times [more in my blog article Double take]. If you need to support IE8 [!!], it's probably best to stick with anonymous function expressions or function declarations, but avoid named function expressions.)

One key thing about a named function expression is that it creates an in-scope identifier with that name for the function within the functon body:

var x = function example() {
    console.log(typeof example); // "function"
};
x();
console.log(typeof example);     // "undefined"