Common utils used in processing arrays

1. given a array that contains empty || null || undefined || false elements

    /**
     *
     * @param arr given an array
     * @returns {Array} return an array that only contains values and true
     */
    remove(arr) {
        /*
            filter(callback) use array provided to create a new array and
            elements in new array must have a value or not null or true.
            if(el) arr.push(el ) "" == true // false " " == true // false
        */
        return arr.filter( (el) => {
            return el;
        });

        // new solution
        return arr.filter(Boolean)

2. Sort an array by obj's property

    // sort an array by obj's property
    /**
     *
     * @param arr given an Object array
     * @param sortBy target property used to compare two elements
     * @param isDesc define the order of the array
     * @returns {Array} return array after sort
     */
    sortObj(arr,sortBy,isDesc) {
        return arr.sort((a,b) => {
            if(isDesc) {
                return (typeof a[sortBy] === "string") ? a[sortBy] < b[sortBy] : b[sortBy] - a[sortBy];
            }else{
                return (typeof a[sortBy] === "string") ? a[sortBy] > b[sortBy] : a[sortBy] - b[sortBy];
            }
        });
    }