diff --git a/src/ui/public/utils/add_word_breaks.js b/src/ui/public/utils/add_word_breaks.js
index 99c35649eedd2..6f2454e93ebe4 100644
--- a/src/ui/public/utils/add_word_breaks.js
+++ b/src/ui/public/utils/add_word_breaks.js
@@ -1,13 +1,13 @@
 define(function () {
   return function addWordBreaks(text, minLineLength) {
     text = text || '';
-    var lineSize = 0;
-    var newText = '';
-    var inHtmlTag = false;
-    var inHtmlChar = false;
+    let lineSize = 0;
+    let newText = '';
+    let inHtmlTag = false;
+    let inHtmlChar = false;
 
-    for (var i = 0, len = text.length; i < len; i++) {
-      var chr = text.charAt(i);
+    for (let i = 0, len = text.length; i < len; i++) {
+      let chr = text.charAt(i);
       newText += chr;
 
       switch (chr) {
diff --git a/src/ui/public/utils/brush_event.js b/src/ui/public/utils/brush_event.js
index 670e8af5eb9de..9ecdc074d784d 100644
--- a/src/ui/public/utils/brush_event.js
+++ b/src/ui/public/utils/brush_event.js
@@ -1,8 +1,8 @@
 import moment from 'moment';
 export default function brushEventProvider(timefilter) {
   return function (event) {
-    var from = moment(event.range[0]);
-    var to = moment(event.range[1]);
+    let from = moment(event.range[0]);
+    let to = moment(event.range[1]);
 
     if (to - from === 0) return;
 
diff --git a/src/ui/public/utils/cidr_mask.js b/src/ui/public/utils/cidr_mask.js
index 88e3e5f27fc9e..a0ae16709538c 100644
--- a/src/ui/public/utils/cidr_mask.js
+++ b/src/ui/public/utils/cidr_mask.js
@@ -1,12 +1,12 @@
 import Ipv4Address from 'ui/utils/ipv4_address';
-var NUM_BITS = 32;
+let NUM_BITS = 32;
 
 function throwError(mask) {
   throw Error('Invalid CIDR mask: ' + mask);
 }
 
 function CidrMask(mask) {
-  var splits = mask.split('\/');
+  let splits = mask.split('\/');
   if (splits.length !== 2) throwError(mask);
   this.initialAddress = new Ipv4Address(splits[0]);
   this.prefixLength = Number(splits[1]);
@@ -14,9 +14,9 @@ function CidrMask(mask) {
 }
 
 CidrMask.prototype.getRange = function () {
-  var variableBits = NUM_BITS - this.prefixLength;
-  var fromAddress = this.initialAddress.valueOf() >> variableBits << variableBits >>> 0; // >>> 0 coerces to unsigned
-  var numAddresses = Math.pow(2, variableBits);
+  let variableBits = NUM_BITS - this.prefixLength;
+  let fromAddress = this.initialAddress.valueOf() >> variableBits << variableBits >>> 0; // >>> 0 coerces to unsigned
+  let numAddresses = Math.pow(2, variableBits);
   return {
     from: new Ipv4Address(fromAddress).toString(),
     to: new Ipv4Address(fromAddress + numAddresses - 1).toString()
diff --git a/src/ui/public/utils/date_math.js b/src/ui/public/utils/date_math.js
index 0c5ccf6e8c679..cefabf4fcc40a 100644
--- a/src/ui/public/utils/date_math.js
+++ b/src/ui/public/utils/date_math.js
@@ -1,11 +1,11 @@
 import _ from 'lodash';
 import moment from 'moment';
 
-var units = ['y', 'M', 'w', 'd', 'h', 'm', 's', 'ms'];
-var unitsAsc = _.sortBy(units, function (unit) {
+let units = ['y', 'M', 'w', 'd', 'h', 'm', 's', 'ms'];
+let unitsAsc = _.sortBy(units, function (unit) {
   return moment.duration(1, unit).valueOf();
 });
-var unitsDesc = unitsAsc.reverse();
+let unitsDesc = unitsAsc.reverse();
 
 /* This is a simplified version of elasticsearch's date parser */
 function parse(text, roundUp) {
@@ -14,7 +14,7 @@ function parse(text, roundUp) {
   if (_.isDate(text)) return moment(text);
 
   let time;
-  var mathString = '';
+  let mathString = '';
   let index;
   let parseString;
 
@@ -42,12 +42,12 @@ function parse(text, roundUp) {
 }
 
 function parseDateMath(mathString, time, roundUp) {
-  var dateTime = time;
-  var i = 0;
-  var len = mathString.length;
+  let dateTime = time;
+  let i = 0;
+  let len = mathString.length;
 
   while (i < len) {
-    var c = mathString.charAt(i++);
+    let c = mathString.charAt(i++);
     let type;
     let num;
     let unit;
@@ -67,7 +67,7 @@ function parseDateMath(mathString, time, roundUp) {
     } else if (mathString.length === 2) {
       num = mathString.charAt(i);
     } else {
-      var numFrom = i;
+      let numFrom = i;
       while (!isNaN(mathString.charAt(i))) {
         i++;
         if (i > 10) return undefined;
diff --git a/src/ui/public/utils/date_range.js b/src/ui/public/utils/date_range.js
index f65a013f4e1c7..4b4b153fbafbf 100644
--- a/src/ui/public/utils/date_range.js
+++ b/src/ui/public/utils/date_range.js
@@ -11,7 +11,7 @@ export default {
     }
   },
   parse: function (rangeString, format) {
-    var chunks = rangeString.split(' to ');
+    let chunks = rangeString.split(' to ');
     if (chunks.length === 2) return {from: moment(chunks[0], format), to: moment(chunks[1], format)};
 
     chunks = rangeString.split('Before ');
diff --git a/src/ui/public/utils/decode_geo_hash.js b/src/ui/public/utils/decode_geo_hash.js
index 0cd65f7c39751..1a1a375c12379 100644
--- a/src/ui/public/utils/decode_geo_hash.js
+++ b/src/ui/public/utils/decode_geo_hash.js
@@ -16,22 +16,22 @@
  * @return {Object} interval
  */
 function decodeGeoHash(geohash) {
-  var BITS = [16, 8, 4, 2, 1];
-  var BASE32 = '0123456789bcdefghjkmnpqrstuvwxyz';
-  var is_even = 1;
-  var lat = [];
-  var lon = [];
+  let BITS = [16, 8, 4, 2, 1];
+  let BASE32 = '0123456789bcdefghjkmnpqrstuvwxyz';
+  let is_even = 1;
+  let lat = [];
+  let lon = [];
   lat[0] = -90.0;
   lat[1] = 90.0;
   lon[0] = -180.0;
   lon[1] = 180.0;
-  var lat_err = 90.0;
-  var lon_err = 180.0;
-  for (var i = 0; i < geohash.length; i++) {
-    var c = geohash[i];
-    var cd = BASE32.indexOf(c);
-    for (var j = 0; j < 5; j++) {
-      var mask = BITS[j];
+  let lat_err = 90.0;
+  let lon_err = 180.0;
+  for (let i = 0; i < geohash.length; i++) {
+    let c = geohash[i];
+    let cd = BASE32.indexOf(c);
+    for (let j = 0; j < 5; j++) {
+      let mask = BITS[j];
       if (is_even) {
         lon_err /= 2;
         refine_interval(lon, cd, mask);
diff --git a/src/ui/public/utils/diff_object.js b/src/ui/public/utils/diff_object.js
index f1e8dd57ea711..25df114df3729 100644
--- a/src/ui/public/utils/diff_object.js
+++ b/src/ui/public/utils/diff_object.js
@@ -3,14 +3,14 @@ import angular from 'angular';
 
 export default function (target, source) {
 
-  var diff = {};
+  let diff = {};
 
   /**
    * Filter the private vars
    * @param {string} key The keys
    * @returns {boolean}
    */
-  var filterPrivateAndMethods = function (obj) {
+  let filterPrivateAndMethods = function (obj) {
     return function (key) {
       if (_.isFunction(obj[key])) return false;
       if (key.charAt(0) === '$') return false;
@@ -18,8 +18,8 @@ export default function (target, source) {
     };
   };
 
-  var targetKeys = _.keys(target).filter(filterPrivateAndMethods(target));
-  var sourceKeys = _.keys(source).filter(filterPrivateAndMethods(source));
+  let targetKeys = _.keys(target).filter(filterPrivateAndMethods(target));
+  let sourceKeys = _.keys(source).filter(filterPrivateAndMethods(source));
 
   // Find the keys to be removed
   diff.removed = _.difference(targetKeys, sourceKeys);
diff --git a/src/ui/public/utils/diff_time_picker_vals.js b/src/ui/public/utils/diff_time_picker_vals.js
index 5aa071f7932bd..43fcfcd5d38d6 100644
--- a/src/ui/public/utils/diff_time_picker_vals.js
+++ b/src/ui/public/utils/diff_time_picker_vals.js
@@ -2,7 +2,7 @@ import _ from 'lodash';
 import angular from 'angular';
 export default function DiffTimePickerValuesFn() {
 
-  var valueOf = function (o) {
+  let valueOf = function (o) {
     if (o) return o.valueOf();
   };
 
diff --git a/src/ui/public/utils/es_bool.js b/src/ui/public/utils/es_bool.js
index a3a9fa9206f89..a580ffac72188 100644
--- a/src/ui/public/utils/es_bool.js
+++ b/src/ui/public/utils/es_bool.js
@@ -1,5 +1,5 @@
 define(function () {
-  var map = {
+  let map = {
     'false': false,
     'off': false,
     'no': false,
@@ -11,7 +11,7 @@ define(function () {
   };
 
   return function (str) {
-    var bool = map[String(str)];
+    let bool = map[String(str)];
 
     if (typeof bool !== 'boolean') {
       throw new TypeError('"' + str + '" does not map to an esBool');
diff --git a/src/ui/public/utils/find_by_param.js b/src/ui/public/utils/find_by_param.js
index fdffd514046b7..60763f07f8478 100644
--- a/src/ui/public/utils/find_by_param.js
+++ b/src/ui/public/utils/find_by_param.js
@@ -3,7 +3,7 @@ import _ from 'lodash';
 // if the param is missing, return undefined
 export default function findByParam(values, param) {
   if (_.isArray(values)) { // point series chart
-    var index = _.findIndex(values, param);
+    let index = _.findIndex(values, param);
     if (index === -1) return;
     return values[index][param];
   }
diff --git a/src/ui/public/utils/ipv4_address.js b/src/ui/public/utils/ipv4_address.js
index d0c8fd3f5f29d..d8c396d02ab6b 100644
--- a/src/ui/public/utils/ipv4_address.js
+++ b/src/ui/public/utils/ipv4_address.js
@@ -1,6 +1,6 @@
 define(function () {
-  var NUM_BYTES = 4;
-  var BYTE_SIZE = 256;
+  let NUM_BYTES = 4;
+  let BYTE_SIZE = 256;
 
   function throwError(ipAddress) {
     throw Error('Invalid IPv4 address: ' + ipAddress);
@@ -19,11 +19,11 @@ define(function () {
     if (typeof ipAddress === 'string') {
       this.value = 0;
 
-      var bytes = ipAddress.split('.');
+      let bytes = ipAddress.split('.');
       if (bytes.length !== NUM_BYTES) throwError(ipAddress);
 
-      for (var i = 0; i < bytes.length; i++) {
-        var byte = Number(bytes[i]);
+      for (let i = 0; i < bytes.length; i++) {
+        let byte = Number(bytes[i]);
         if (!isIntegerInRange(byte, 0, BYTE_SIZE)) throwError(ipAddress);
         this.value += Math.pow(BYTE_SIZE, NUM_BYTES - 1 - i) * byte;
       }
@@ -33,9 +33,9 @@ define(function () {
   }
 
   Ipv4Address.prototype.toString = function () {
-    var value = this.value;
-    var bytes = [];
-    for (var i = 0; i < NUM_BYTES; i++) {
+    let value = this.value;
+    let bytes = [];
+    for (let i = 0; i < NUM_BYTES; i++) {
       bytes.unshift(value % 256);
       value = Math.floor(value / 256);
     }
diff --git a/src/ui/public/utils/mapping_setup.js b/src/ui/public/utils/mapping_setup.js
index 5ec4d28a69327..232fa5ff21072 100644
--- a/src/ui/public/utils/mapping_setup.js
+++ b/src/ui/public/utils/mapping_setup.js
@@ -2,9 +2,9 @@ import angular from 'angular';
 import _ from 'lodash';
 define(function () {
   return function MappingSetupService(kbnIndex, es) {
-    var mappingSetup = this;
+    let mappingSetup = this;
 
-    var json = {
+    let json = {
       _serialize: function (val) {
         if (val != null) return angular.toJson(val);
       },
@@ -16,14 +16,14 @@ define(function () {
     /**
      * Use to create the mappings, but that should only happen one at a time
      */
-    var activeTypeCreations = {};
+    let activeTypeCreations = {};
 
     /**
      * Get the list of type's mapped in elasticsearch
      * @return {[type]} [description]
      */
-    var getKnownKibanaTypes = _.once(function () {
-      var indexName = kbnIndex;
+    let getKnownKibanaTypes = _.once(function () {
+      let indexName = kbnIndex;
       return es.indices.getFieldMapping({
         // only concerned with types in this kibana index
         index: indexName,
@@ -70,13 +70,13 @@ define(function () {
         });
       }
 
-      var prom = getKnownKibanaTypes()
+      let prom = getKnownKibanaTypes()
       .then(function (knownTypes) {
         // if the type is in the knownTypes array already
         if (~knownTypes.indexOf(type)) return false;
 
         // we need to create the mapping
-        var body = {};
+        let body = {};
         body[type] = {
           properties: mapping
         };
diff --git a/src/ui/public/utils/no_white_space.js b/src/ui/public/utils/no_white_space.js
index 29c4392cc8f3d..c57cc58fcb95d 100644
--- a/src/ui/public/utils/no_white_space.js
+++ b/src/ui/public/utils/no_white_space.js
@@ -1,4 +1,4 @@
-var TAGS_WITH_WS = />\s+</g;
+let TAGS_WITH_WS = />\s+</g;
 
 /**
  * Remove all of the whitespace between html tags
diff --git a/src/ui/public/utils/obj_define.js b/src/ui/public/utils/obj_define.js
index 0084ae72bf692..664c6fcfb2168 100644
--- a/src/ui/public/utils/obj_define.js
+++ b/src/ui/public/utils/obj_define.js
@@ -9,7 +9,7 @@ function ObjDefine(defaults, prototype) {
 }
 
 ObjDefine.REDEFINE_SUPPORTED = (function () {
-  var a = Object.create(Object.prototype, {
+  let a = Object.create(Object.prototype, {
     prop: {
       configurable: true,
       value: 1
@@ -66,7 +66,7 @@ ObjDefine.prototype.comp = function (name, val) {
  * @return {object} - created object
  */
 ObjDefine.prototype.create = function () {
-  var self = this;
+  let self = this;
   self.obj = Object.create(this.prototype, self.descs);
 
   if (!ObjDefine.REDEFINE_SUPPORTED && !self.prototype.toJSON) {
@@ -76,7 +76,7 @@ ObjDefine.prototype.create = function () {
     // due to https://github.com/ariya/phantomjs/issues/11856
     self.obj.toJSON = function () {
       return _.transform(self.obj, function (json, val, key) {
-        var desc = self.descs[key];
+        let desc = self.descs[key];
         if (desc && desc.enumerable && val == null) return;
         json[key] = val;
       }, {});
@@ -97,8 +97,8 @@ ObjDefine.prototype._define = function (name, val, exported, changeable) {
 };
 
 ObjDefine.prototype._describe = function (name, val, exported, changeable) {
-  var self = this;
-  var exists = val != null;
+  let self = this;
+  let exists = val != null;
 
   if (exported && ObjDefine.REDEFINE_SUPPORTED) {
     return {
diff --git a/src/ui/public/utils/ordinal_suffix.js b/src/ui/public/utils/ordinal_suffix.js
index c7d14d437cff6..54038effa2bd9 100644
--- a/src/ui/public/utils/ordinal_suffix.js
+++ b/src/ui/public/utils/ordinal_suffix.js
@@ -5,12 +5,12 @@ export default function addOrdinalSuffix(num) {
 };
 
 function suffix(num) {
-  var int = Math.floor(parseFloat(num));
+  let int = Math.floor(parseFloat(num));
 
-  var hunth = int % 100;
+  let hunth = int % 100;
   if (hunth >= 11 && hunth <= 13) return 'th';
 
-  var tenth = int % 10;
+  let tenth = int % 10;
   if (tenth === 1) return 'st';
   if (tenth === 2) return 'nd';
   if (tenth === 3) return 'rd';
diff --git a/src/ui/public/utils/parse_interval.js b/src/ui/public/utils/parse_interval.js
index 1f46eaf6a33bf..9c81c730e10df 100644
--- a/src/ui/public/utils/parse_interval.js
+++ b/src/ui/public/utils/parse_interval.js
@@ -3,18 +3,18 @@ import moment from 'moment';
 import dateMath from 'ui/utils/date_math';
 
 // Assume interval is in the form (value)(unit), such as "1h"
-var INTERVAL_STRING_RE = new RegExp('^([0-9\\.]*)\\s*(' + dateMath.units.join('|') + ')$');
+let INTERVAL_STRING_RE = new RegExp('^([0-9\\.]*)\\s*(' + dateMath.units.join('|') + ')$');
 
 export default function parseInterval(interval) {
-  var matches = String(interval).trim().match(INTERVAL_STRING_RE);
+  let matches = String(interval).trim().match(INTERVAL_STRING_RE);
 
   if (!matches) return null;
 
   try {
-    var value = parseFloat(matches[1]) || 1;
-    var unit = matches[2];
+    let value = parseFloat(matches[1]) || 1;
+    let unit = matches[2];
 
-    var duration = moment.duration(value, unit);
+    let duration = moment.duration(value, unit);
 
     // There is an error with moment, where if you have a fractional interval between 0 and 1, then when you add that
     // interval to an existing moment object, it will remain unchanged, which causes problems in the ordered_x_keys
@@ -23,7 +23,7 @@ export default function parseInterval(interval) {
     // adding 0.5 days until we hit the end date. However, since there is a bug in moment, when you add 0.5 days to
     // the start date, you get the same exact date (instead of being ahead by 12 hours). So instead of returning
     // a duration corresponding to 0.5 hours, we return a duration corresponding to 12 hours.
-    var selectedUnit = _.find(dateMath.units, function (unit) {
+    let selectedUnit = _.find(dateMath.units, function (unit) {
       return Math.abs(duration.as(unit)) >= 1;
     });
 
diff --git a/src/ui/public/utils/query_string.js b/src/ui/public/utils/query_string.js
index df317284e0095..adf714cd64030 100644
--- a/src/ui/public/utils/query_string.js
+++ b/src/ui/public/utils/query_string.js
@@ -1,4 +1,4 @@
-var qs = {};
+let qs = {};
 
 /*****
 /*** orignally copied from angular, modified our purposes
@@ -37,7 +37,7 @@ function encodeUriQuery(val, pctEncodeSpaces) {
  * @returns {Object.<string,boolean|Array>}
  */
 qs.decode = function (keyValue) {
-  var obj = {};
+  let obj = {};
   let keyValueParts;
   let key;
 
@@ -46,7 +46,7 @@ qs.decode = function (keyValue) {
       keyValueParts = keyValue.split('=');
       key = tryDecodeURIComponent(keyValueParts[0]);
       if (key !== void 0) {
-        var val = keyValueParts[1] !== void 0 ? tryDecodeURIComponent(keyValueParts[1]) : true;
+        let val = keyValueParts[1] !== void 0 ? tryDecodeURIComponent(keyValueParts[1]) : true;
         if (!obj[key]) {
           obj[key] = val;
         } else if (Array.isArray(obj[key])) {
@@ -66,10 +66,10 @@ qs.decode = function (keyValue) {
  * @return {String}
  */
 qs.encode = function (obj) {
-  var parts = [];
-  var keys = Object.keys(obj).sort();
+  let parts = [];
+  let keys = Object.keys(obj).sort();
   keys.forEach(function (key) {
-    var value = obj[key];
+    let value = obj[key];
     if (Array.isArray(value)) {
       value.forEach(function (arrayValue) {
         parts.push(qs.param(key, arrayValue));
@@ -92,8 +92,8 @@ qs.param = function (key, val) {
  *                    the same if the url does not have a query string
  */
 qs.findInUrl = function (url) {
-  var qsStart = url.indexOf('?');
-  var hashStart = url.lastIndexOf('#');
+  let qsStart = url.indexOf('?');
+  let hashStart = url.lastIndexOf('#');
 
   if (hashStart === -1) {
     // out of bounds
@@ -111,8 +111,8 @@ qs.findInUrl = function (url) {
 };
 
 qs.replaceParamInUrl = function (url, param, newVal) {
-  var loc = qs.findInUrl(url);
-  var parsed = qs.decode(url.substring(loc.start + 1, loc.end));
+  let loc = qs.findInUrl(url);
+  let parsed = qs.decode(url.substring(loc.start + 1, loc.end));
 
   if (newVal != null) {
     parsed[param] = newVal;
@@ -120,7 +120,7 @@ qs.replaceParamInUrl = function (url, param, newVal) {
     delete parsed[param];
   }
 
-  var chars = url.split('');
+  let chars = url.split('');
   chars.splice(loc.start, loc.end - loc.start, '?' + qs.encode(parsed));
   return chars.join('');
 };
diff --git a/src/ui/public/utils/range.js b/src/ui/public/utils/range.js
index b272fdfa9ae01..dc34e4ab650e0 100644
--- a/src/ui/public/utils/range.js
+++ b/src/ui/public/utils/range.js
@@ -13,7 +13,7 @@ import _ from 'lodash';
  *
  * @type {String}
  */
-var _RE_NUMBER = '(\\-?(?:\\d+(?:\\.\\d+)?|Infinity))';
+let _RE_NUMBER = '(\\-?(?:\\d+(?:\\.\\d+)?|Infinity))';
 
 /**
  * Regexp for the interval notation
@@ -25,11 +25,11 @@ var _RE_NUMBER = '(\\-?(?:\\d+(?:\\.\\d+)?|Infinity))';
  *
  * @type {RegExp}
  */
-var RANGE_RE = new RegExp('^\\s*([\\[|\\(])\\s*' + _RE_NUMBER + '\\s*,\\s*' + _RE_NUMBER + '\\s*([\\]|\\)])\\s*$');
+let RANGE_RE = new RegExp('^\\s*([\\[|\\(])\\s*' + _RE_NUMBER + '\\s*,\\s*' + _RE_NUMBER + '\\s*([\\]|\\)])\\s*$');
 
 function parse(input) {
 
-  var match = String(input).match(RANGE_RE);
+  let match = String(input).match(RANGE_RE);
   if (!match) {
     throw new TypeError('expected input to be in interval notation eg. (100, 200]');
   }
@@ -43,7 +43,7 @@ function parse(input) {
 }
 
 function Range(/* minIncl, min, max, maxIncl */) {
-  var args = _.toArray(arguments);
+  let args = _.toArray(arguments);
   if (args[1] > args[2]) args.reverse();
 
   this.minInclusive = args[0];
diff --git a/src/ui/public/utils/sequencer.js b/src/ui/public/utils/sequencer.js
index 15be808dd0022..5656890c8f101 100644
--- a/src/ui/public/utils/sequencer.js
+++ b/src/ui/public/utils/sequencer.js
@@ -1,18 +1,18 @@
 import _ from 'lodash';
 
 function create(min, max, length, mod) {
-  var seq = new Array(length);
+  let seq = new Array(length);
 
-  var valueDist = max - min;
+  let valueDist = max - min;
 
   // range of values that the mod creates
-  var modRange = [mod(0, length), mod(length - 1, length)];
+  let modRange = [mod(0, length), mod(length - 1, length)];
 
   // distance between
-  var modRangeDist = modRange[1] - modRange[0];
+  let modRangeDist = modRange[1] - modRange[0];
 
   _.times(length, function (i) {
-    var modIPercent = (mod(i, length) - modRange[0]) / modRangeDist;
+    let modIPercent = (mod(i, length) - modRange[0]) / modRangeDist;
 
     // percent applied to distance and added to min to
     // produce value
@@ -80,8 +80,8 @@ export default {
     // adapted from output of http://www.timotheegroleau.com/Flash/experiments/easing_function_generator.htm
     // generates numbers from 0 to 100
 
-    var ts = (i /= length) * i;
-    var tc = ts * i;
+    let ts = (i /= length) * i;
+    let tc = ts * i;
     return 100 * (
       0.5 * tc * ts +
       -3 * ts * ts +
diff --git a/src/ui/public/utils/simple_emitter.js b/src/ui/public/utils/simple_emitter.js
index 20cc5569b8a8b..f9a6f69a24eee 100644
--- a/src/ui/public/utils/simple_emitter.js
+++ b/src/ui/public/utils/simple_emitter.js
@@ -20,7 +20,7 @@ function SimpleEmitter() {
  * @return {SimpleEmitter} - this, for chaining
  */
 SimpleEmitter.prototype.on = function (name, handler) {
-  var handlers = this._listeners[name];
+  let handlers = this._listeners[name];
   if (!handlers) handlers = this._listeners[name] = [];
 
   handlers.push(handler);
@@ -68,8 +68,8 @@ SimpleEmitter.prototype.removeAllListeners = function () {
  */
 SimpleEmitter.prototype.emit = _.restParam(function (name, args) {
   if (!this._listeners[name]) return this;
-  var listeners = this.listeners(name);
-  var i = -1;
+  let listeners = this.listeners(name);
+  let i = -1;
 
   while (++i < listeners.length) {
     listeners[i].apply(this, args);
diff --git a/src/ui/public/utils/slugify_id.js b/src/ui/public/utils/slugify_id.js
index 3cc4366a53964..b0f1920e501e6 100644
--- a/src/ui/public/utils/slugify_id.js
+++ b/src/ui/public/utils/slugify_id.js
@@ -2,14 +2,14 @@ import _ from 'lodash';
 export default function (id) {
   if (id == null) return;
 
-  var trans = {
+  let trans = {
     '/' : '-slash-',
     '\\?' : '-questionmark-',
     '\\&' : '-ampersand-',
     '=' : '-equal-'
   };
   _.each(trans, function (val, key) {
-    var regex = new RegExp(key, 'g');
+    let regex = new RegExp(key, 'g');
     id = id.replace(regex, val);
   });
   id = id.replace(/[\s]+/g, '-');
diff --git a/src/ui/public/utils/supports.js b/src/ui/public/utils/supports.js
index 3e99b42da0104..cf8cd4835c65f 100644
--- a/src/ui/public/utils/supports.js
+++ b/src/ui/public/utils/supports.js
@@ -5,14 +5,14 @@ import _ from 'lodash';
  */
 export default {
   cssFilters: (function () {
-    var e = document.createElement('img');
-    var rules = ['webkitFilter', 'mozFilter', 'msFilter', 'filter'];
-    var test = 'grayscale(1)';
+    let e = document.createElement('img');
+    let rules = ['webkitFilter', 'mozFilter', 'msFilter', 'filter'];
+    let test = 'grayscale(1)';
     rules.forEach(function (rule) { e.style[rule] = test; });
 
     document.body.appendChild(e);
-    var styles = window.getComputedStyle(e);
-    var can = _(styles).pick(rules).includes(test);
+    let styles = window.getComputedStyle(e);
+    let can = _(styles).pick(rules).includes(test);
     document.body.removeChild(e);
 
     return can;