Clean up some of the vars and loops.

There's zero reason in 2015 to use a loop, or "var" - this cleans some of them up.

There's still a bunch left, but I figured I'd tackle just a little bit at a time.

RegExp.make.js

@@ -37,7 +37,8 @@ RegExp.make = (function () {
     if (0x20 <= n && n <= 0x7e) {
       return String.fromCharCode(n).replace(UNSAFE_CHARS_CHARSET, '\\$&');
     }
-    var hex = n.toString(16);
+    /** @type {string} */
+    const hex = n.toString(16);
     return '\\u0000'.substring(0, 6 - hex.length) + hex;
   }
 
@@ -87,23 +88,16 @@ RegExp.make = (function () {
    * @this {!CharRanges}
    */
   CharRanges.prototype.toString = function () {
-    var s = '';
-    /** @type {!Array.<number>}. */
-    const ranges = this.ranges;
-    /** @type {number} */
-    const n = ranges.length;
-    for (var i = 0; i < n; ++i) {
-      /** @type {number} */
-      const leftAndSpan = ranges[i];
+    return this.ranges.reduce(function (s, leftAndSpan) {
       const left = leftAndSpan >> 16;
       const span = leftAndSpan & 0xffff;
       s += encodeRangeEndPoint(left);
       if (span) {
         if (span !== 1) { s += '-'; }
         s += encodeRangeEndPoint(left + span);
       }
-    }
-    return s;
+      return s;
+    }, '');
   };
   /**
    * The minimum code-point matched or NaN.
@@ -125,9 +119,8 @@ RegExp.make = (function () {
    * @return {!CharRanges} this to allow chaining.
    */
   CharRanges.prototype.addRange = function (left, opt_right) {
-    var right = opt_right || left;
+    const right = +(opt_right || left);
     left = +left;
-    right = +right;
     if ('number' !== typeof left
         || left < 0 || right > MAX_CHAR_IN_RANGE || left > right
         || left % 1 || right % 1) {
@@ -160,12 +153,9 @@ RegExp.make = (function () {
     /** @type {!Array.<number>} */
     const ranges = this.ranges;
     /** @type {number} */
-    const n = ranges.length;
-    var pastLastRight = 0;
+    let pastLastRight = 0;
     const invertedRanges = [];
-    for (var i = 0; i < n; ++i) {
-      /** @type {number} */
-      const leftAndSpan = ranges[i];
+    ranges.forEach(function (leftAndSpan) {
       const left = leftAndSpan >> 16;
       const span = leftAndSpan & 0xFFFF;
       if (pastLastRight < left) {
@@ -175,7 +165,7 @@ RegExp.make = (function () {
         );
       }
       pastLastRight = left + span + 1;
-    }
+    });
     if (pastLastRight <= MAX_CHAR_IN_RANGE) {
       invertedRanges.push(
         (pastLastRight << 16)
@@ -229,14 +219,8 @@ RegExp.make = (function () {
    * @return {!CharRanges} a newly allocated output.  Not modified in place.
    */
   CharRanges.prototype.intersectionWithRange = function (min, max) {
-    /** @type {!Array.<number>} */
-    const ranges = this.ranges;
     const intersection = new CharRanges();
-    /** @type {number} */
-    const n = ranges.length;
-    for (var i = 0; i < n; ++i) {
-      /** @type {number} */
-      const leftAndSpan = ranges[i];
+    this.ranges.forEach(function (leftAndSpan) {
       const left = leftAndSpan >> 16;
       const span = leftAndSpan & 0xFFFF;
       /** @type {number} */
@@ -245,7 +229,7 @@ RegExp.make = (function () {
       if (!(left > max || right < min)) {
         intersection.addRange(Math.max(min, left), Math.min(max, right));
       }
-    }
+    });
     return intersection;
   };
   /**
@@ -265,19 +249,13 @@ RegExp.make = (function () {
    * @this {!CharRanges}
    */
   CharRanges.prototype.forEachRange = function (callback) {
-    /** @type {!Array.<number>} */
-    const ranges = this.ranges;
-    /** @type {number} */
-    const n = ranges.length;
-    for (var i = 0; i < n; ++i) {
-      /** @type {number} */
-      const leftAndSpan = ranges[i];
+    this.ranges.forEach(function (leftAndSpan) {
       const left = leftAndSpan >> 16;
       const span = leftAndSpan & 0xFFFF;
       /** @type {number} */
       const right = left + span;
       callback(left, right);
-    }
+    });
   };
   CharRanges.prototype.clear = function () {
     this.ranges.length = 0;