Add streamToJson helper

helpers/json.js

@@ -0,0 +1,33 @@
+import fs from 'fs'
+
+// Write JSON to file via stream
+// so that we can handle large JSON files
+// that would not normal fit into memory
+// or V8 string size limits
+export function streamToJson ( dataArray, filePath ) {
+    return new Promise( resolve => {
+        const output = fs.createWriteStream( filePath, 'utf8' )
+
+        // When the stream is finished
+        output.on( 'finish', () => {
+            resolve( output )
+        })
+    
+        // Write opening array bracket
+        output.write( '[' )
+
+        // Write each item in the array
+        for ( const item of dataArray ) {
+            output.write( JSON.stringify( item ) + ',' )
+        }
+
+        // Write closing array bracket
+        output.write( ']' )
+
+        // Close the stream
+        output.end()
+
+        // Return the stream
+        return output
+    })
+}