function areaOfFigures([arg1, arg2, arg3, arg4]){

    let figure = toString(arg1);

    if (figure === "square"){
        let a = parseFloat(arg2);
        area = a * a;
        console.log(area.toFixed(3));
    } else if (figure === "rectangle"){
        let a = parseFloat(arg2);
        let b = parseFloat(arg3);
        area = a * b;
        console.log(area.toFixed(3));
    } else if (figure === "circle"){
        let r = parseFloat(arg4);
        area = r * r * Math.PI;
        console.log(area.toFixed(3));
    } else if (figure === "triangle"){
        let a = parseFloat(arg2);
        let b = parseFloat(arg3);
        area = (a * b)/2;
        console.log(area.toFixed(3));
    }
}

areaOfFigures (square, 5);