How do I set text from variable into a another variable?

[Nikolas]

I have JS code . How to set the contents (text) of the [[LIST_WITH_FILE_CONTENT]] variable
in the variable

let list = 

instead of this text

When I consider every thing that grows
Holds in perfection but a little moment,
Vaunt in their youthful sap, at height decrease,
And wear their brave state out of memory

In this JS-code:

let list = `When I consider every thing that grows
Holds in perfection but a little moment,
Vaunt in their youthful sap, at height decrease,
And wear their brave state out of memory`.split('\n');
 
for(let i = 0, temp = []; i < list.length; i++) {
    if(temp.includes(list[i].toLowerCase())) {
        list.splice(i, 1);
        i--;
    } else {
        temp.push(list[i].toLowerCase());
    }
}
 
console.log(list);
[[LIST_WITH_FILE_CONTENT]]=list;

I tried putting it that way, but I get the error TypeError: _BAS_VARIABLES.LIST_WITH_FILE_CONTENT.filter.split is not a function
Here's how, but I get an error:

let list = [[LIST_WITH_FILE_CONTENT]].split('\n');
 
for(let i = 0, temp = []; i < list.length; i++) {
    if(temp.includes(list[i].toLowerCase())) {
        list.splice(i, 1);
        i--;
    } else {
        temp.push(list[i].toLowerCase());
    }
}
 
console.log(list);
[[LIST_WITH_FILE_CONTENT]]=list;