Example.
Step 1 : Create field storage.
\Drupal\field\Entity\FieldStorageConfig::create(array(
'field_name' => 'field_text',
'entity_type' => 'node',
'type' => 'text',
'cardinality' => -1,
By editor, 12 January, 2017
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By editor, 3 January, 2017