Merge pull request rstudio#1830 from rstudio/wch-compare-version

Add Shiny.compareVersion() function

Author: jcheng5

NEWS.md

@@ -9,7 +9,7 @@ shiny 1.0.5.9000
 
 ### Minor new features and improvements
 
-* The version of Shiny is now accessible from Javascript, with `Shiny.version`. ([#1826](https://github.com/rstudio/shiny/pull/1826))
+* The version of Shiny is now accessible from Javascript, with `Shiny.version`. There is also a new function for comparing version strings, `Shiny.compareVersion()`. ([#1826](https://github.com/rstudio/shiny/pull/1826), [#1830](https://github.com/rstudio/shiny/pull/1830))
 
 * Addressed [#1784](https://github.com/rstudio/shiny/issues/1784): `runApp()` will avoid port 6697, which is considered unsafe by Chrome.
 

inst/www/shared/shiny.js

@@ -286,6 +286,42 @@ function equal(...args) {
   return true;
 };
 
+// Compare version strings like "1.0.1", "1.4-2". `op` must be a string like
+// "==" or "<".
+exports.compareVersion = function(a, op, b) {
+  function versionParts(ver) {
+    return (ver + "")
+      .replace(/-/, ".")
+      .replace(/(\.0)+[^\.]*$/, "")
+      .split(".");
+  }
+
+  function cmpVersion(a, b) {
+    a = versionParts(a);
+    b = versionParts(b);
+    var len = Math.min(a.length, b.length);
+    var cmp;
+
+    for(var i=0; i<len; i++) {
+      cmp = parseInt(a[i], 10) - parseInt(b[i], 10);
+      if(cmp !== 0) {
+        return cmp;
+      }
+    }
+    return a.length - b.length;
+  }
+
+  var diff = cmpVersion(a, b);
+
+  if (op === "==")      return (diff === 0);
+  else if (op === ">=") return (diff >=  0);
+  else if (op === ">")  return (diff >   0);
+  else if (op === "<=") return (diff <=  0);
+  else if (op === "<")  return (diff <   0);
+  else                  throw `Unknown operator: ${op}`;
+};
+
+
 // multimethod: Creates functions — "multimethods" — that are polymorphic on one
 // or more of their arguments.
 //