let parentObject = {
    initVal:10,
    addInitVal: () => {
        this.initVal += 1;
    },
    getVal: () => {
        return this.initVal;
    }
}
console.log(parentObject.initVal); //returns 10
parentObject.addInitVal(); //add by 1
console.log(parentObject.initVal); //still 10 ????
console.log(parentObject.getVal()); //returns NaN ????

let parentObject = {
    initVal:10,
    addInitVal: function(){
        this.initVal += 1;
    },
    getVal: function(){
        return this.initVal;
    }
}
console.log(parentObject.initVal); //returns 10
parentObject.addInitVal(); //add by 1
console.log(parentObject.initVal); //returns 11
console.log(parentObject.getVal()); //returns 11