const scrollTop = document.documentElement.scrollTop
scroll bar event, drag the scroll bar to print the scrollTop with different values each time! Didn"t you say the value can"t be changed? Why is this okay?
const scrollTop = document.documentElement.scrollTop
scroll bar event, drag the scroll bar to print the scrollTop with different values each time! Didn"t you say the value can"t be changed? Why is this okay?
if you just define it in the function, because the function has scope, that is, when the function is executed, the variable will be automatically destroyed, and when it is called again, the variable will be defined again, so the value has changed not because of modification, but because of redefinition.
of course, if it is an object, the
my understanding is that the
document.documentElement.scrollTop exists in a memory address, even though it is a const definition. The variable declared by
const points to this address, and the value of the address has changed, but the pointer to const has not changed.
this actually involves primitive type and reference type
const defines a constant, and the value of a constant cannot be modified
take string among the six primitive types as an example
const a = '1';
a = '2'; // => take object among the three reference types as an example
const a = {b: 1};
a.b = 2; // =>
a = 2; // => a.b is actually a modification to b. But it has no effect on a Previous: What are the problems encountered when using iview to modify the default style in vue?
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