Source

File: wp-includes/class.wp-dependencies.php

public function enqueue( $handles ) {
		foreach ( (array) $handles as $handle ) {
			$handle = explode( '?', $handle );

			if ( ! in_array( $handle[0], $this->queue, true ) && isset( $this->registered[ $handle[0] ] ) ) {
				$this->queue[] = $handle[0];

				// Reset all dependencies so they must be recalculated in recurse_deps().
				$this->all_queued_deps = null;

				if ( isset( $handle[1] ) ) {
					$this->args[ $handle[0] ] = $handle[1];
				}
			}
		}
	}