Method getDuplicate

src/danfojs-base/shared/utils.ts:709–734

* Get duplicate values in a array * @param arr

(arr: Array<T>)

     * @param arr 
     */
    getDuplicate<T>(arr: Array<T>) {
        const tempObj: any = {};
        const resultObj: any = {};

        for (let i = 0; i < arr.length; i++) {
            const val = arr[i];
            if (this.keyInObject(tempObj, val as unknown as string | number)) {
                tempObj[val]["count"] += 1;
                tempObj[val]["index"].push(i);
            } else {
                tempObj[val] = {};
                tempObj[val]["count"] = 1;
                tempObj[val]["index"] = [i];
            }
        }

        for (let key in tempObj) {
            if (tempObj[key]["count"] >= 2) {
                resultObj[key] = {};
                resultObj[key]["count"] = tempObj[key]["count"];
                resultObj[key]["index"] = tempObj[key]["index"];
            }
        }

        return resultObj;
    }

    /**
     * Returns the index of a sorted array