Sort by field

sortBy.js

function sortBy(arr, fields) {
    if (typeof fields === 'string') fields = [fields];
    function compareFn(a, b) {
      return fields
        .map(field => {
          let dir = 1;
          if (field[0] === "-") {
            dir = -1;
            field = field.substring(1);
          }
          return a[field] > b[field] ? dir : a[field] < b[field] ? -dir : 0;
        })
        .reduce((p, n) => (p ? p : n), 0);
    }
    return arr.slice().sort(compareFn);
}