JSFiddle - React, Tailwind, and code Playground

JavaScript

var x=' ', y='#', i=0, line=0;

// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for

for (i /*раз*/; i <= 8; i++) {
    for (line /*два*/; line <=8; line ++) {
        if (i %2==0) {
            if ( line %2==0) console.log(x);
            else (console.log(y));
        }
        else if (i %2!=0) {
            if ( line %2!=0) console.log(y);
            else (console.log(x));
        }
    }
}