code: function sign(value) {
      let sign = NaN;
  
      if (_.isNumber(value)) {
          if (value === 0) {
              sign = value;
          }
          else if (value >= 1) {
              sign = 1;
          }
          else if (value <= -1) {
              sign = -1;
          }
      }
  
      return sign;
  }
docs: Returns a number representing the sign of `value`.
  
  If `value` is a positive number, negative number, positive zero or negative zero,
  the function will return 1, -1, 0 or -0 respectively. Otherwise, NaN is returned.
  
  @static
  @memberOf _
  @category Math
  @param {number} value A number
  @returns {number} A number representing the sign
  @example
  
  _.sign(10);
  // => 1
  
  _.sign(-10);
  // => -1