feat: Added support for inline currentScript calls in IE and Edge (#5)

  - Fixed a few linting issues
  - Reworked performance-relevant parts of the code
  - Added .editorconfig

.editorconfig

@@ -0,0 +1,3 @@
+[*]
+indent_style = space
+indent_size = 2

currentScript.js

@@ -2,27 +2,54 @@
 
 // MIT license
 
-(function(document){
-  var currentScript = "currentScript",
-      scripts = document.getElementsByTagName('script'); // Live NodeList collection
+(function (document) {
+  var currentScript = 'currentScript';
 
   // If browser needs currentScript polyfill, add get currentScript() to the document object
   if (!(currentScript in document)) {
     Object.defineProperty(document, currentScript, {
-      get: function(){
-
-        // IE 6-10 supports script readyState
-        // IE 10+ support stack trace
-        try { throw new Error(); }
+      get: function () {
+        // IE 8-10 support script readyState
+        // IE 11+ support stack trace
+        try {
+          throw new Error();
+        }
         catch (err) {
-
           // Find the second match for the "at" string to get file src url from stack.
           // Specifically works with the format of stack traces in IE.
-          var i, res = ((/.*at [^\(]*\((.*):.+:.+\)$/ig).exec(err.stack) || [false])[1];
+          var i = 0,
+            stackDetails = (/.*at [^(]*\((.*):(.+):(.+)\)$/ig).exec(err.stack),
+            scriptLocation = (stackDetails && stackDetails[1]) || false,
+            line = (stackDetails && stackDetails[2]) || false,
+            currentLocation = document.location.href.replace(document.location.hash, ''),
+            pageSource,
+            inlineScriptSourceRegExp,
+            inlineScriptSource,
+            scripts = document.getElementsByTagName('script'); // Live NodeList collection
+
+          if (scriptLocation === currentLocation) {
+            pageSource = document.documentElement.outerHTML;
+            inlineScriptSourceRegExp = new RegExp('(?:[^\\n]+?\\n){0,' + (line - 2) + '}[^<]*<script>([\\d\\D]*?)<\\/script>[\\d\\D]*', 'i');
+            inlineScriptSource = pageSource.replace(inlineScriptSourceRegExp, '$1').trim();
+          }
+
+          for (; i < scripts.length; i++) {
+            // If ready state is interactive, return the script tag
+            if (scripts[i].readyState === 'interactive') {
+              return scripts[i];
+            }
+
+            // If src matches, return the script tag
+            if (scripts[i].src === scriptLocation) {
+              return scripts[i];
+            }
 
-          // For all scripts on the page, if src matches or if ready state is interactive, return the script tag
-          for(i in scripts){
-            if(scripts[i].src == res || scripts[i].readyState == "interactive"){
+            // If inline source matches, return the script tag
+            if (
+              scriptLocation === currentLocation &&
+              scripts[i].innerHTML &&
+              scripts[i].innerHTML.trim() === inlineScriptSource
+            ) {
               return scripts[i];
             }
           }