feat: add option strict that throws an error if the input is not va…

…lid JSON (#11)

README.md

@@ -36,6 +36,24 @@ import destr from 'https://deno.land/x/destr/src/index.ts'
 console.log(destr('{ "deno": "yay" }'))
 ```
 
+### Options
+
+`destr` allows the following options as the second argument:
+
+#### `strict`
+
+Default: `false`
+
+If set to `true`, `destr` will throw an error if the input is not a valid JSON string or parsing fails.
+
+```js
+// Returns "[foo"
+destr('[foo')
+
+// Throws an error
+destr('[foo', { strict: true })
+```
+
 ## Why?
 
 Please note that `destr` is little bit slower when parsing a standard JSON string mainly because of transform to avoid [prototype pollution](https://hueniverse.com/a-tale-of-prototype-poisoning-2610fa170061) which can lead to serious security issues if not being sanitized. In the other words, `destr` is better when input is not always a json string or from untrusted source like request body.

src/index.ts

@@ -12,7 +12,11 @@ function jsonParseTransform (key: string, value: any): any {
   return value
 }
 
-export default function destr (val: any): any {
+export type Options = {
+  strict?: boolean
+}
+
+export default function destr (val: any, options: Options = {}): any {
   if (typeof val !== 'string') {
     return val
   }
@@ -26,6 +30,9 @@ export default function destr (val: any): any {
   if (_lval === 'undefined') { return undefined }
 
   if (!JsonSigRx.test(val)) {
+    if (options.strict) {
+      throw new SyntaxError('Invalid JSON')
+    }
     return val
   }
 
@@ -34,7 +41,10 @@ export default function destr (val: any): any {
       return JSON.parse(val, jsonParseTransform)
     }
     return JSON.parse(val)
-  } catch (_e) {
+  } catch (error) {
+    if (options.strict) {
+      throw error
+    }
     return val
   }
 }