Extract findStringProperty() function

Author: Turbo87

lib/transform.js

@@ -139,32 +139,26 @@ function isMethod(path, name) {
   return node.type === 'ObjectMethod' && node.key.type === 'Identifier' && node.key.name === name;
 }
 
-function findTagName(properties) {
-  let tagNameProperty = properties.filter(path => isProperty(path, 'tagName'))[0];
-  if (!tagNameProperty) {
-    return 'div';
+function findStringProperty(properties, name, defaultValue = null) {
+  let propertyPath = properties.filter(path => isProperty(path, name))[0];
+  if (!propertyPath) {
+    return defaultValue;
   }
 
-  let elementIdPath = tagNameProperty.get('value');
-  if (elementIdPath.value.type !== 'StringLiteral') {
-    throw new SilentError(`Unexpected \`tagName\` value: ${j(elementIdPath).toSource()}`);
+  let valuePath = propertyPath.get('value');
+  if (valuePath.value.type !== 'StringLiteral') {
+    throw new SilentError(`Unexpected \`${name}\` value: ${j(valuePath).toSource()}`);
   }
 
-  return elementIdPath.value.value;
+  return valuePath.value.value;
 }
 
-function findElementId(properties) {
-  let elementIdProperty = properties.filter(path => isProperty(path, 'elementId'))[0];
-  if (!elementIdProperty) {
-    return null;
-  }
-
-  let elementIdPath = elementIdProperty.get('value');
-  if (elementIdPath.value.type !== 'StringLiteral') {
-    throw new SilentError(`Unexpected \`elementId\` value: ${j(elementIdPath).toSource()}`);
-  }
+function findTagName(properties) {
+  return findStringProperty(properties, 'tagName', 'div');
+}
 
-  return elementIdPath.value.value;
+function findElementId(properties) {
+  return findStringProperty(properties, 'elementId');
 }
 
 function findAttributeBindings(properties) {