TypeError: nines.slice is not a function at-CodePudding

If I input this in the console it outputs correct result:

'99' - '99'.slice(1)  
=> 90

But when I do this in a loop, it throws error, why?

let len = 4;
let nines = '9';
let sum = 0;
for (let i = 1; i < len   1; i  ) { 
    sum  = i * (nines - nines.slice(1));
    nines =  9;
}

Uncaught TypeError: nines.slice is not a function
    at <anonymous>:5:28

CodePudding user response：

i think it's a typo

nines =  9;

should be

nines  = 9;

CodePudding user response：

nines = 9 sets nines to 9. Did you mean nines = '9'

CodePudding user response：

It was a typo, should be = 9. I didn't notice it as my attention was focused on the error message which pointed at slice.