_unique = function (src) {
		if (Array.from && Set) {
			return Array.from(new Set(src));
		}

		if (_areAllUnique(src)) {
			return src.slice();
		}

		// A faster unique method is to use object keys to identify used values,
		// but this doesn't work with arrays or objects, which we must also
		// consider. See jsperf.app/compare-array-unique-versions/4 for more
		// information.
		var
			out = [],
			val,
			i, ien = src.length,
			j, k = 0;

		again: for (i = 0; i < ien; i++) {
			val = src[i];

			for (j = 0; j < k; j++) {
				if (out[j] === val) {
					continue again;
				}
			}

			out.push(val);
			k++;
		}

		return out;
	}
Find the unique elements in a source array.

@param  {array} src Source array
@return {array} Array of unique items
@ignore