Use builtin Array.find rather than array.nth where applicable.

common/content/abbreviations.js

@@ -105,7 +105,7 @@ var AbbrevHive = Class("AbbrevHive", Contexts.Hive, {
     },
 
     /** @property {boolean} True if there are no abbreviations. */
-    get empty() !values(this._store).nth(util.identity, 0),
+    get empty() !values(this._store).find(util.identity),
 
     /**
      * Adds a new abbreviation.
@@ -251,7 +251,7 @@ var Abbreviations = Module("abbreviations", {
         let match = this._match.exec(text);
         if (match)
             return this.hives.map(h => h.get(mode, match[2] || match[4] || match[6]))
-                       .nth(util.identity, 0);
+                       .find(util.identity);
         return null;
     },
 

common/content/commandline.js

@@ -2018,7 +2018,7 @@ var ItemList = Class("ItemList", {
         if (start < 0 || start >= this.itemCount)
             return null;
 
-        group = array.nth(groups, g => let (i = start - g.offsets.start) i >= 0 && i < g.itemCount, 0);
+        group = groups.find(g => let (i = start - g.offsets.start) i >= 0 && i < g.itemCount);
         return [group.context, start - group.offsets.start];
     },
 

common/content/hints.js

@@ -1299,16 +1299,21 @@ var Hints = Module("hints", {
             },
             {
                 keepQuotes: true,
+
                 getKey: function (val, default_)
-                    let (res = array.nth(this.value, re => let (match = re.exec(val)) match && match[0] == val, 0))
-                        res ? res.matcher : default_,
+                    let (res = this.value.find(re => let (match = re.exec(val)) match && match[0] == val))
+                        res ? res.matcher
+                            : default_,
+
                 parse: function parse(val) {
                     let vals = parse.supercall(this, val);
                     for (let value in values(vals))
                         value.matcher = DOM.compileMatcher(Option.splitList(value.result));
                     return vals;
                 },
+
                 testValues: function testValues(vals, validator) vals.every(re => Option.splitList(re).every(validator)),
+
                 validator: DOM.validateMatcher
             });
 

common/content/modes.js

@@ -274,7 +274,8 @@ var Modes = Module("modes", {
     remove: function remove(mode, covert) {
         if (covert && this.topOfStack.main != mode) {
             util.assert(mode != this.NORMAL);
-            for (let m; m = array.nth(this.modeStack, m => m.main == mode, 0);)
+
+            for (let m; m = this.modeStack.find(m => m.main == mode);)
                 this._modeStack.splice(this._modeStack.indexOf(m));
         }
         else if (this.stack.some(m => m.main == mode)) {
@@ -604,7 +605,7 @@ var Modes = Module("modes", {
 
             getKey: function getKey(val, default_) {
                 if (isArray(val))
-                    return (array.nth(this.value, v => val.some(m => m.name === v.mode), 0)
+                    return (this.value.find(v => val.some(m => m.name === v.mode))
                                 || { result: default_ }).result;
 
                 return hasOwnProperty(this.valueMap, val) ? this.valueMap[val] : default_;

common/content/tabs.js

@@ -550,7 +550,7 @@ var Tabs = Module("tabs", {
         if (matches)
             return tabs.select(this.allTabs[parseInt(matches[1], 10) - 1], false);
 
-        matches = array.nth(tabs.allTabs, t => (t.linkedBrowser.lastURI || {}).spec === buffer, 0);
+        matches = tabs.allTabs.find(t => (t.linkedBrowser.lastURI || {}).spec === buffer);
         if (matches)
             return tabs.select(matches, false);