diff --git a/common/custom.js b/common/custom.js
new file mode 100644
index 0000000..b7a99b0
--- /dev/null
+++ b/common/custom.js
@@ -0,0 +1,21 @@
+/**
+ * This is just a simple version of deep copy
+ * Has a lot of edge cases bug
+ * If you want to use a perfect deep copy, use lodash's _.cloneDeep
+ * @param {Object} source
+ * @returns {Object}
+ */
+export function deepClone(source) {
+  if (!source && typeof source !== 'object') {
+    throw new Error('error arguments', 'deepClone')
+  }
+  const targetObj = source.constructor === Array ? [] : {}
+  Object.keys(source).forEach(keys => {
+    if (source[keys] && typeof source[keys] === 'object') {
+      targetObj[keys] = deepClone(source[keys])
+    } else {
+      targetObj[keys] = source[keys]
+    }
+  })
+  return targetObj
+}
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