Improve network error detection across browsers (#152)

* Improve network error detection across browsers

* extra semicolons removed

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Co-authored-by: Shulga, Ruslan X <ruslan.x.shulga@chase.com>

lib/index.js

@@ -74,7 +74,13 @@ class Backend {
     this.options.request(this.options, url, payload, (err, res) => {
       if (res && ((res.status >= 500 && res.status < 600) || !res.status)) return callback('failed loading ' + url + '; status code: ' + res.status, true /* retry */)
       if (res && res.status >= 400 && res.status < 500) return callback('failed loading ' + url + '; status code: ' + res.status, false /* no retry */)
-      if (!res && err && err.message && (err.message.toLowerCase().indexOf('failed') > -1 && (err.message.indexOf('fetch') > -1 || err.message.toLowerCase().indexOf('network') > -1))) return callback('failed loading ' + url + ': ' + err.message, true /* retry */)
+      if (!res && err && err.message) {
+        const errorMessage = err.message.toLowerCase()
+        const isNetworkError = errorMessage.includes('failed') || errorMessage.includes('fetch') || errorMessage.includes('network') || errorMessage.includes('load')
+        if (isNetworkError) {
+          return callback('failed loading ' + url + ': ' + err.message, true /* retry */)
+        }
+      }
       if (err) return callback(err, false)
 
       let ret, parseErr