refactor: more efficient flatten (#222)

Author: gajus

Diff for: package.json

@@ -57,7 +57,9 @@
   ],
   "license": "BSD-3-Clause",
   "main": "./dist/src/index.js",
-  "files": ["dist/src/"],
+  "files": [
+    "dist/src/"
+  ],
   "name": "table",
   "repository": {
     "type": "git",

Diff for: src/utils.ts

@@ -124,7 +124,13 @@ export const extractTruncates = (config: BaseConfig): number[] => {
 };
 
 export const flatten = <T>(array: T[][]): T[] => {
-  return ([] as T[]).concat(...array);
+  const destination = [];
+  const arrayLength = array.length;
+  for (let index = 0; index < arrayLength; index++) {
+    destination.push(...array[index]);
+  }
+
+  return destination;
 };
 
 export const calculateRangeCoordinate = (spanningCellConfig: SpanningCellConfig): RangeCoordinate => {