Use template literals for string interpolation

lib/persistence.js

@@ -215,7 +215,8 @@ class Persistence {
     lineStream.on('end', () => {
       // A bit lenient on corruption
       if (length > 0 && corruptItems / length > this.corruptAlertThreshold) {
-        const err = new Error('More than ' + Math.floor(100 * this.corruptAlertThreshold) + '% of the data file is corrupt, the wrong beforeDeserialization hook may be used. Cautiously refusing to start NeDB to prevent dataloss')
+        const corruptPercent = Math.floor(100 * this.corruptAlertThreshold)
+        const err = new Error(`More than ${corruptPercent}% of the data file is corrupt, the wrong beforeDeserialization hook may be used. Cautiously refusing to start NeDB to prevent dataloss`)
         cb(err, null)
         return
       }