var x = 1;
function foo(x, y = function() { x = 2; }) {
var x = 3;
y();
console.log(x);
}
foo() // 3
x // 1 if the function assigned by y is externally defined, why is the last global x 1 ;
why does, foo () print 3 if the function assigned by y is internally defined;
Hey, your observation is correct. This scope is neither "outside" nor "inside", but a scope sandwiched in the middle to prevent the default parameters from being contaminated by variables inside the function.
you need to take a good look at the default values of function parameters in ES6. Recommend a book: " learn more about ES6 ".
in ES6, the default value of the parameter is equivalent to expanding directly:
The code is interesting, but it may not be used much in the actual project.
secondly, this is a closure.
as mentioned above
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