JSFiddle - React, Tailwind, and code Playground

JavaScript

var defaults = {
    title: undefined,
    yMax: undefined,
    yMin: undefined,
    yPeriod: undefined,
    xMax: undefined,
    xMin: undefined,
    xPeriod: undefined,
    dots: {}
  };
 
var arr = [];
for(key in defaults) {
	if(typeof defaults[key] !== "object") {
  	arr.push(key);
  }
}

alert(arr);