feat(url): add a beta updateOnEveryKeystroke option (#1779)

Updating the url bar constantly may be a challenge for some OS +
browsers (OSX, chrome), I want to push this option and see if it's
better for users.

Author: vvo

src/lib/url-sync.js

@@ -95,6 +95,7 @@ class URLSync {
     this.mapping = options.mapping || {};
     this.getHistoryState = options.getHistoryState || (() => null);
     this.threshold = options.threshold || 700;
+    this.updateOnEveryKeyStroke = options.updateOnEveryKeyStroke || true;
     this.trackedParameters = options.trackedParameters || ['query', 'attribute:*', 'index', 'page', 'hitsPerPage'];
 
     this.searchParametersFromUrl = AlgoliaSearchHelper
@@ -146,11 +147,19 @@ class URLSync {
       }
     );
 
-    if (this.timer() < this.threshold) {
-      this.urlUtils.replaceState(qs, {getHistoryState: this.getHistoryState});
-    } else {
-      this.urlUtils.pushState(qs, {getHistoryState: this.getHistoryState});
+    if (this.updateOnEveryKeyStroke === true) {
+      if (this.timer() < this.threshold) {
+        this.urlUtils.replaceState(qs, {getHistoryState: this.getHistoryState});
+      } else {
+        this.urlUtils.pushState(qs, {getHistoryState: this.getHistoryState});
+      }
+      return;
     }
+
+    clearTimeout(this.urlUpdateTimeout);
+    this.urlUpdateTimeout = setTimeout(() => {
+      this.urlUtils.pushState(qs, {getHistoryState: this.getHistoryState});
+    }, this.threshold);
   }
 
   // External API's