var arr = [];

for (var i = 0; i < 5; i++) {
    arr[i] = [];
    for (var j = 0; j < 5; j++) {
        let random = Math.random();
        if(random >= 0.5){
            arr[i][j] = true;
        }else{
            arr[i][j] = false;
        }
    }
}

console.dir(arr);