fix: uses Object.assign instead of spreading

Author: artem-zakharchenko

lib/units/normalize/normalizeHeaders.js

@@ -20,13 +20,13 @@ const normalizeHeaders = (headers) => {
   }
 
   return Object.keys(headers).reduce(
-    (normalizedHeaders, name) => ({
-      ...normalizedHeaders,
-      [name.toLowerCase()]:
-        typeof headers[name] === 'string'
-          ? normalizeStringValue(headers[name])
-          : headers[name]
-    }),
+    (normalizedHeaders, name) =>
+      Object.assign({}, normalizedHeaders, {
+        [name.toLowerCase()]:
+          typeof headers[name] === 'string'
+            ? normalizeStringValue(headers[name])
+            : headers[name]
+      }),
     {}
   );
 };

lib/utils/evolve.js

@@ -38,7 +38,9 @@ const evolve = (schema, { strict = false } = {}) => (data) => {
         : value;
     /* eslint-enable no-nested-ternary */
 
-    return isArray ? acc.concat(nextValue) : { ...acc, [key]: nextValue };
+    return isArray
+      ? acc.concat(nextValue)
+      : Object.assign({}, acc, { [key]: nextValue });
   };
 
   const nextData = Object.keys(data).reduce(reducer, result);

package-lock.json

@@ -80,10 +80,9 @@ Make sure it's in the "Header-Name: value" format.
 
       const [_, key, value] = match;
 
-      return {
-        ...acc,
+      return Object.assign({}, acc, {
         [key.toLowerCase()]: value.trim()
-      };
+      });
     }, {});
     return headers;
   }