Edit in JSFiddle

var arr_len = 10; // length of input array

function random_array( num ) {
    var i, j, tmp,
        raw_array = [];

    for ( i = 0; i < num; i++ ) { // create array
        raw_array.push(i);
    }

    for ( i = num - 1; i > 0; i-- ) { // swap elements in array randomly using Fisher-Yates (aka Knuth) Shuffle
        j = Math.floor( Math.random() * (i + 1) );
        tmp = raw_array[i];
        raw_array[i] = raw_array[j];
        raw_array[j] = tmp;
    }
    //alert( 'n = ' + num + '; array = [ ' + raw_array + ' ]' ); // alert for demonstation
    document.getElementById('log').innerHTML = 'n = ' + num + '; array = [ ' + raw_array + ' ]';
    // return raw_array;
}

random_array( arr_len );

<div id="log"></div>