How to draw js hollow graphics quickly

/*空心直角三角形*/

    for (var i = 0; i < 10; i++) {

        (i == 0 || i == 9) ? document.write(Array(i + 2).join("* ") + "
") : document.write("*" + Array(i + 1).join("   ") + "*
");

    }

    /*空心菱形*/

    var arr = [];

    for (var p = 0; p < 6; p++) {

        (p == 0) ? arr.push(Array(6).join("   ") + "*
") : arr.push(Array(6 - p).join("   ") + "*" + Array(p * 2 + 1).join("   ") + "*
");

    }

    (document.write(arr.join("")), arr.pop(), document.write(arr.reverse().join("")));