Gerar caracteres aleatórios JavaScript

function geraStringAleatoria(tamanho) {
    var stringAleatoria = '';
    var caracteres = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    for (var i = 0; i < tamanho; i++) {
        stringAleatoria += caracteres.charAt(Math.floor(Math.random() * caracteres.length));
    }
    return stringAleatoria;
}

console.log(geraStringAleatoria(8)); // PQjN0tnQ