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))
+                    let (res = this.value.find(re => let (match = re.exec(val)) match && match[0] == val))
-                        res ? res.matcher : default_,
+                        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);
 

common/modules/base.jsm

@@ -1508,21 +1508,21 @@ update(iter, {
 
     every: function every(iter, pred, self) {
         pred = pred || util.identity;
-        for (let elem in iter)
+        for (let elem of iter)
             if (!pred.call(self, elem))
                 return false;
         return true;
     },
     some: function every(iter, pred, self) {
         pred = pred || util.identity;
-        for (let elem in iter)
+        for (let elem of iter)
             if (pred.call(self, elem))
                 return true;
         return false;
     },
 
     filter: function filter(iter, pred, self) {
-        for (let elem in iter)
+        for (let elem of iter)
             if (pred.call(self, elem))
                 yield elem;
     },
@@ -1536,13 +1536,13 @@ update(iter, {
      * @param {object} self The this object for *fn*.
      */
     forEach: function forEach(iter, func, self) {
-        for (let val in iter)
+        for (let val of iter)
             func.call(self, val);
     },
 
     indexOf: function indexOf(iter, elem) {
         let i = 0;
-        for (let item in iter) {
+        for (let item of iter) {
             if (item == elem)
                 return i;
             i++;
@@ -1558,7 +1558,7 @@ update(iter, {
      * @returns {Array}
      */
     map: function map(iter, func, self) {
-        for (let i in iter)
+        for (let i of iter)
             yield func.call(self, i);
     },
 
@@ -1570,18 +1570,29 @@ update(iter, {
         if (typeof pred === "number")
             [pred, n] = [() => true, pred]; // Hack.
 
-        for (let elem in iter)
+        for (let elem of iter)
             if (pred.call(self, elem) && n-- === 0)
                 return elem;
         return undefined;
     },
 
+    /**
+     * Analog of Array.find method. Returns the first item in the
+     * iterator for which `pred` returns true.
+     */
+    find: function find(iter, pred, self) {
+        for (let elem of iter)
+            if (pred.call(self, elem))
+                return elem;
+        return undefined;
+    },
+
     sort: function sort(iter, fn, self)
         array(this.toArray(iter).sort(fn, self)),
 
     uniq: function uniq(iter) {
         let seen = RealSet();
-        for (let item in iter)
+        for (let item of iter)
             if (!seen.add(item))
                 yield item;
     },

common/modules/buffer.jsm

@@ -2476,10 +2476,9 @@ var Buffer = Module("Buffer", {
                             if (/^func:/.test(filter.result))
                                 var res = dactyl.userEval("(" + Option.dequote(filter.result.substr(5)) + ")")(doc, line);
                             else
-                                res = iter.nth(filter.matcher(doc),
+                                res = iter.find(filter.matcher(doc),
                                                 elem => ((elem.nodeValue || elem.textContent).trim() == line &&
-                                                        DOM(elem).display != "none"),
+                                                         DOM(elem).display != "none"))
-                                               0)
                                    || iter.nth(filter.matcher(doc), util.identity, line - 1);
                             if (res)
                                 break;

common/modules/commands.jsm

@@ -622,11 +622,12 @@ var CommandHive = Class("CommandHive", Contexts.Hive, {
      */
     get: function get(name, full) {
         let cmd = this._map[name]
-               || !full && array.nth(this._list, cmd => cmd.hasName(name), 0)
+               || !full && this._list.find(cmd => cmd.hasName(name))
                || null;
 
         if (!cmd && full) {
-            let name = array.nth(this.specs, spec => Command.hasName(spec, name), 0);
+            // Hrm. This is wrong. -Kris
+            let name = this._specs.find(spec => Command.hasName(spec, name));
             return name && this.get(name);
         }
 
@@ -883,7 +884,7 @@ var Commands = Module("commands", {
      * @returns {Command}
      */
     get: function get(name, full) iter(this.hives).map(([i, hive]) => hive.get(name, full))
-                                                  .nth(util.identity, 0),
+                                                  .find(util.identity),
 
     /**
      * Returns true if a command invocation contains a URL referring to the

common/modules/config.jsm

@@ -243,7 +243,7 @@ var ConfigBase = Class("ConfigBase", {
     bestLocale: function (list) {
         return values([this.appLocale, this.appLocale.replace(/-.*/, ""),
                        "en", "en-US", list[0]])
-            .nth((function (l) this.has(l)).bind(RealSet(list)), 0);
+            .find(bind("has", RealSet(list)));
     },
 
     /**

common/modules/contexts.jsm

@@ -67,8 +67,9 @@ var Group = Class("Group", {
 }, {
     compileFilter: function (patterns, default_=false) {
         function siteFilter(uri)
-            let (match = array.nth(siteFilter.filters, f => f(uri), 0))
+            let (match = siteFilter.filters.find(f => f(uri)))
-                match ? match.result : default_;
+                match ? match.result
+                      : default_;
 
         return update(siteFilter, {
             toString: function () this.filters.join(","),
@@ -205,12 +206,10 @@ var Contexts = Module("contexts", {
     Context: function Context(file, group, args) {
         const { contexts, io, newContext, plugins, userContext } = this.modules;
 
-        let isPlugin  = array.nth(io.getRuntimeDirectories("plugins"),
+        let isPlugin  = io.getRuntimeDirectories("plugins")
-                                  dir => dir.contains(file, true),
+                          .find(dir => dir.contains(file, true));
-                                  0);
+        let isRuntime = io.getRuntimeDirectories("")
-        let isRuntime = array.nth(io.getRuntimeDirectories(""),
+                          .find(dir => dir.contains(file, true));
-                                  dir => dir.contains(file, true),
-                                  0);
 
         let name = isPlugin ? file.getRelativeDescriptor(isPlugin).replace(File.PATH_SEP, "-")
                             : file.leafName;
@@ -308,9 +307,8 @@ var Contexts = Module("contexts", {
         if (uri instanceof Ci.nsIFileURL)
             var file = File(uri.file);
 
-        let isPlugin = array.nth(io.getRuntimeDirectories("plugins"),
+        let isPlugin = io.getRuntimeDirectories("plugins")
-                                 dir => dir.contains(file, true),
+                         .find(dir => dir.contains(file, true));
-                                 0);
 
         let name = isPlugin && file && file.getRelativeDescriptor(isPlugin)
                                            .replace(File.PATH_SEP, "-");

common/modules/downloads.jsm

@@ -157,7 +157,7 @@ var Download = Class("Download", {
         let val = this._compare[order.substr(1)](this, other);
 
         return (order[0] == "-") ? -val : val;
-    }, this).nth(util.identity, 0) || 0,
+    }, this).find(util.identity) || 0,
 
     timeRemaining: Infinity,
 

common/modules/options.jsm

@@ -1504,8 +1504,7 @@ var Options = Module("options", {
 
             function val(obj) {
                 if (isArray(opt.defaultValue)) {
-                    let val = array.nth(obj, re => (re.key == extra.key),
+                    let val = Array.find(obj, re => (re.key == extra.key));
-                                        0);
                     return val && val.result;
                 }
                 if (hasOwnProperty(opt.defaultValue, extra.key))

common/modules/sanitizer.jsm

@@ -474,7 +474,10 @@ var Sanitizer = Module("sanitizer", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakRef
                         sanitizer.sanitize(items, range);
                 }
 
-                if (array.nth(opt.value, i => i == "all" || /^!/.test(i), 0) == "all" && !args["-host"])
+                if ("all" == opt.value.find(i => (i == "all" ||
+                                                  /^!/.test(i)))
+                    && !args["-host"])
+
                     modules.commandline.input(_("sanitize.prompt.deleteAll") + " ",
                         function (resp) {
                             if (resp.match(/^y(es)?$/i)) {
@@ -620,8 +623,7 @@ var Sanitizer = Module("sanitizer", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakRef
                 },
 
                 has: function has(val)
-                    let (res = array.nth(this.value, v => (v == "all" || v.replace(/^!/, "") == val),
+                    let (res = this.value.find(v => (v == "all" || v.replace(/^!/, "") == val)))
-                                         0))
                         res && !/^!/.test(res),
 
                 validator: function (values) values.length &&

common/modules/styles.jsm

@@ -277,8 +277,7 @@ var Styles = Module("Styles", {
     },
 
     addHive: function addHive(name, ref, persist) {
-        let hive = array.nth(this.hives, h => h.name === name,
+        let hive = this.hives.find(h => h.name === name);
-                             0);
         if (!hive) {
             hive = Hive(name, persist);
             this.hives.push(hive);