pattern-generator.js

function patternGenerator(rows, symbol1, symbol2, symbol3) {
    for (let index = 0; index < rows; index++) {

        // (1) this is step one print symbol blank
        var space = "";
        for (let indexj = 0; indexj < (rows - index - 1); indexj++) {
            space += symbol3;
        }

        // (2) this is step two print symbol oval
        var oval = "";
        for (let indexk = 0; indexk < (index + 1); indexk++) {
            oval += symbol1;
        }

        // (3) this is step three print symbol x
        var x = "";
        var mid = (rows / 2) - 2;
        for (let indexl = 0; indexl < index; indexl++) {

            if (indexl > mid) {
                x += symbol2;
            } else {
                x += symbol1;
            }
        }

        // print several step
        console.log(space + oval + x);
    }
}

// call function
patternGenerator(6, "o", "x", " ");