Merge branch 'development' into feature/portal-ledger-support

* development: (437 commits)
  Publish
  Update yarn.lock
  Update the CHANGELOG
  Fix the bug making it impossible to specify the custom ZRX address
  Fix fill/cancel order by looking for NoError instead of empty blockchainErr given the BlockchainErrs type refactor
  Add a comment about a yarn bug
  Add our mainnet and kovan nodes as backups for Portal requests
  Fix bug hiding the user info from topBar
  Add dev-utils package to top level README
  Prettier newline
  Prettier
  Allow Token symbols to be alphanumeric
  Update CHANGELOG, rebase on development
  Should not -> cannot
  Reject negative amounts in isValidBaseUnitAmount
  Re-add changelog for 0x.js
  Fix prettier
  Update yarn.lock
  Move tests to a separate folder
  Change file layout
  ...

# Conflicts:
#	packages/website/README.md

1 files changed, 37 insertions, 0 deletions

diff --git a/packages/utils/src/interval_utils.ts b/packages/utils/src/interval_utils.ts
new file mode 100644
index 000000000..ebecc7015
--- /dev/null
+++ b/packages/utils/src/interval_utils.ts
@@ -0,0 +1,37 @@
+import * as _ from 'lodash';
+
+export const intervalUtils = {
+    setAsyncExcludingInterval(fn: () => Promise<void>, intervalMs: number, onError: (err: Error) => void) {
+        let locked = false;
+        const intervalId = setInterval(async () => {
+            if (locked) {
+                return;
+            } else {
+                locked = true;
+                try {
+                    await fn();
+                } catch (err) {
+                    onError(err);
+                }
+                locked = false;
+            }
+        }, intervalMs);
+        return intervalId;
+    },
+    clearAsyncExcludingInterval(intervalId: NodeJS.Timer): void {
+        clearInterval(intervalId);
+    },
+    setInterval(fn: () => void, intervalMs: number, onError: (err: Error) => void) {
+        const intervalId = setInterval(() => {
+            try {
+                fn();
+            } catch (err) {
+                onError(err);
+            }
+        }, intervalMs);
+        return intervalId;
+    },
+    clearInterval(intervalId: NodeJS.Timer): void {
+        clearInterval(intervalId);
+    },
+};