functional

src/util.ts

@@ -2,3 +2,43 @@ export type JSONDataTypes = string | number | boolean
 export type JSONObject<Value = JSONDataTypes, Key extends string = string> = {
     [key in Key]: Value
 }
+
+export function defaultJson(data: string, defaultValue: string | JSONObject = '') {
+
+    if (data.length === 0) {
+        //no existing data, give the default value instead
+
+        if (typeof defaultValue === 'string') {
+            return defaultValue
+        } else {
+            return JSON.stringify(defaultValue)
+        }
+
+    } else if (typeof defaultValue !== 'string') {
+        //existing data should be compared
+        //nothing to compare if default value is string
+
+        try {
+            let foundJson = JSON.parse(data)
+
+            for (let key in defaultValue) {
+                if (
+                    !(key in foundJson) ||
+                    typeof foundJson[key] !== typeof defaultValue[key]
+                ) {
+                    //key doesnt exist OR key exists, but type is incorrect
+                    foundJson[key] = defaultValue[key]
+                }
+            }
+
+            return JSON.stringify(foundJson)
+        } catch (e) {
+            //couldn't parse data
+            return JSON.stringify(defaultValue)
+        }
+
+    }
+
+    return data
+
+}