//
(function(){
var x = c = b = {a:1}
})()
console.log(x.a); // error , x is not defined
console.log(c,b) // {a: 1} {a: 1}
Why is x.a undefined here
//
(function(){
var x = c = b = {a:1}
})()
console.log(x.a); // error , x is not defined
console.log(c,b) // {a: 1} {a: 1}
Why is x.a undefined here
this involves the knowledge of variable scope enhancement:
var x = c = b = {ahol1} is equivalent to
b = {a:1}; //var
c = b; //var
var x = c; if you use the var keyword, this variable will only take effect within the function that defines it. Without the var keyword, this variable is promoted to a global variable.
therefore, an error is reported directly when using x.a directly outside, because in the external scope, x is not defined at all, let alone x.a. C and b are global variables that can be accessed.
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