function fromPairs(pairs) {
      var index = -1,
          length = pairs == null ? 0 : pairs.length,
          result = {};

      while (++index < length) {
        var pair = pairs[index];
        result[pair[0]] = pair[1];
      }
      return result;
    }
The inverse of `_.toPairs`; this method returns an object composed
from key-value `pairs`.

@static
@memberOf _
@since 4.0.0
@category Array
@param {Array} pairs The key-value pairs.
@returns {Object} Returns the new object.
@example

_.fromPairs([['a', 1], ['b', 2]]);
// => { 'a': 1, 'b': 2 }