checkHover () {
        if (simulationArea.mouseDown) return;
        for (let i = 0; i < this.nodeList.length; i++) {
            this.nodeList[i].checkHover();
        }
        if (!simulationArea.mouseDown) {
            if (simulationArea.hover === this) {
                this.hover = this.isHover();
                if (!this.hover) simulationArea.hover = undefined;
            } else if (!simulationArea.hover) {
                this.hover = this.isHover();
                if (this.hover) simulationArea.hover = this;
            } else {
                this.hover = false;
            }
        }
    }
check hover over the element
@return {boolean}