Make cache-busting optional

Closes #70

README.md

@@ -382,6 +382,12 @@ It's called every time a page is switched, even for history buttons.
 
 Value (in px) to scrollTo when a page is switched.
 
+##### `cacheBust` (Boolean, default true)
+
+When set to true,
+append a timestamp query string segment to the requested URLs
+in order to skip browser cache.
+
 ##### `debug` (Boolean, default to false)
 
 Enable verbose mode & doesn't use fallback when there is an error.

lib/proto/parse-options.js

@@ -19,6 +19,7 @@ module.exports = function(options){
     }
   }
   this.options.scrollTo = (typeof this.options.scrollTo === 'undefined') ? 0 : this.options.scrollTo;
+  this.options.cacheBust = (typeof this.options.cacheBust === 'undefined') ? true : this.options.cacheBust
   this.options.debug = this.options.debug || false
 
   // we can’t replace body.outerHTML or head.outerHTML

lib/request.js

@@ -12,7 +12,12 @@ module.exports = function(location, callback) {
     }
   }
 
-  request.open("GET", location + (!/[?&]/.test(location) ? "?" : "&") + (new Date().getTime()), true)
+  // Add a timestamp as part of the query string if cache busting is enabled
+  if (this.options.cacheBust) {
+    location += (!/[?&]/.test(location) ? "?" : "&") + new Date().getTime()
+  }
+
+  request.open("GET", location, true)
   request.setRequestHeader("X-Requested-With", "XMLHttpRequest")
   request.send(null)
   return request

tests/lib/proto/parse-options.js

@@ -46,6 +46,7 @@ tape("test parse initalization options function", function(t) {
     t.deepEqual(typeof body_1.options.analytics,"function");
 
     t.deepEqual(body_1.options.scrollTo,0);
+    t.deepEqual(body_1.options.cacheBust,true);
     t.deepEqual(body_1.options.debug,false);
     t.end();
   });

tests/lib/request.js

@@ -3,8 +3,14 @@ var tape = require("tape")
 var request = require("../../lib/request.js")
 
 tape("test xhr request", function(t) {
-  t.test("- request is made and gets a result", function(t) {
-    request("https://api.github.com/", function(result) {
+  t.test("- request is made, gets a result, and is cache-busted", function(t) {
+    var requestCacheBust = request.bind({
+      options: {
+        cacheBust: true,
+      },
+    });
+    var r = requestCacheBust("https://api.github.com/", function(result) {
+      t.equal(r.responseURL.indexOf("?"), 23, "XHR URL is cache-busted when configured to be")
       try {
         result = JSON.parse(result)
       }
@@ -15,5 +21,16 @@ tape("test xhr request", function(t) {
       t.end()
     })
   })
+  t.test("- request is not cache-busted when configured not to be", function(t) {
+    var requestNoCacheBust = request.bind({
+      options: {
+        cacheBust: false,
+      },
+    });
+    var r = requestNoCacheBust("https://api.github.com/", function() {
+      t.equal(r.responseURL, "https://api.github.com/", "XHR URL is left untouched")
+      t.end()
+    })
+  })
   t.end()
 })