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Consider the following code:
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function getList() {
	return ['a', 'b', 'c'];
};

// get the list
const list=getList();

// rotate an item in the list
list.push(list.shift());

// output the list
console.log(1,list);

// outout the list returned by getList()
console.log(2,getList());
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No.1 and No.2 list are different.
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Now consider this code:
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function getList() {
	// the following the initalization of the list runs only the first time.
	const list=['a', 'b', 'c'];

	// redefine the getList function
	getList=function(){return list;}

	// return the getList function
	return getList();
}

// get the list
const list=getList();

// rotate an item in the list
list.push(list.shift());

// output the list
console.log(1,list);

// outout the list returned by getList()
console.log(2,getList());
--------------------------------------------
This time No.1 and No.2 list are the same.
because the inializaion runs only one time.
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