diff --git a/.eslintrc.yml b/.eslintrc.yml
index f8ed3b2c3..7fc6b7b44 100644
--- a/.eslintrc.yml
+++ b/.eslintrc.yml
@@ -1,6 +1,7 @@
 extends: eslint:recommended
 parserOptions:
   ecmaVersion: 6
+  sourceType: module
 env:
   node: true
   browser: true
@@ -24,7 +25,6 @@ rules:
   no-trailing-spaces: 2
   no-use-before-define: [2, nofunc]
   semi: 0
-  strict: [2, global]
   valid-jsdoc: [2, requireReturn: false]
   no-control-regex: 0
   no-useless-escape: 2
diff --git a/lib/ajv.js b/lib/ajv.js
index 32147440d..cf3264541 100644
--- a/lib/ajv.js
+++ b/lib/ajv.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var compileSchema = require("./compile"),
   resolve = require("./compile/resolve"),
   Cache = require("./cache"),
@@ -27,10 +25,10 @@ Ajv.prototype._compile = _compile
 
 Ajv.prototype.compileAsync = require("./compile/async")
 var customKeyword = require("./keyword")
-Ajv.prototype.addKeyword = customKeyword.add
-Ajv.prototype.getKeyword = customKeyword.get
-Ajv.prototype.removeKeyword = customKeyword.remove
-Ajv.prototype.validateKeyword = customKeyword.validate
+Ajv.prototype.addKeyword = customKeyword.addKeyword
+Ajv.prototype.getKeyword = customKeyword.getKeyword
+Ajv.prototype.removeKeyword = customKeyword.removeKeyword
+Ajv.prototype.validateKeyword = customKeyword.validateKeyword
 
 var errorClasses = require("./compile/error_classes")
 Ajv.ValidationError = errorClasses.Validation
diff --git a/lib/cache.js b/lib/cache.js
index 2539362d2..b970862ef 100644
--- a/lib/cache.js
+++ b/lib/cache.js
@@ -1,5 +1,3 @@
-"use strict"
-
 module.exports = Cache
 
 function Cache() {
diff --git a/lib/compile/async.js b/lib/compile/async.js
index bb758d767..270b9df07 100644
--- a/lib/compile/async.js
+++ b/lib/compile/async.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var MissingRefError = require("./error_classes").MissingRef
 
 module.exports = compileAsync
diff --git a/lib/compile/equal.js b/lib/compile/equal.js
index 4d060f849..b67591643 100644
--- a/lib/compile/equal.js
+++ b/lib/compile/equal.js
@@ -1,5 +1,3 @@
-"use strict"
-
 // do NOT remove this file - it would break pre-compiled schemas
 // https://github.com/ajv-validator/ajv/issues/889
 module.exports = require("fast-deep-equal")
diff --git a/lib/compile/error_classes.js b/lib/compile/error_classes.js
index cd6f59a5f..32cdf81e9 100644
--- a/lib/compile/error_classes.js
+++ b/lib/compile/error_classes.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var resolve = require("./resolve")
 
 module.exports = {
diff --git a/lib/compile/index.js b/lib/compile/index.js
index 2eb4750d2..3757e6d2c 100644
--- a/lib/compile/index.js
+++ b/lib/compile/index.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var resolve = require("./resolve"),
   util = require("./util"),
   errorClasses = require("./error_classes"),
diff --git a/lib/compile/resolve.js b/lib/compile/resolve.js
index 73891d270..78e270825 100644
--- a/lib/compile/resolve.js
+++ b/lib/compile/resolve.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var URI = require("uri-js"),
   equal = require("fast-deep-equal"),
   util = require("./util"),
diff --git a/lib/compile/rules.js b/lib/compile/rules.js
index b54dc2dca..12ffa6630 100644
--- a/lib/compile/rules.js
+++ b/lib/compile/rules.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var ruleModules = require("../dotjs"),
   toHash = require("./util").toHash
 
@@ -9,16 +7,14 @@ module.exports = function rules() {
       type: "number",
       rules: ["multipleOf", "format"],
     },
-    {type: "string", rules: ["maxLength", "minLength", "pattern", "format"]},
+    {type: "string", rules: ["pattern", "format"]},
     {
       type: "array",
-      rules: ["maxItems", "minItems", "items", "contains", "uniqueItems"],
+      rules: ["items", "contains", "uniqueItems"],
     },
     {
       type: "object",
       rules: [
-        "maxProperties",
-        "minProperties",
         "required",
         "dependencies",
         "propertyNames",
diff --git a/lib/compile/schema_obj.js b/lib/compile/schema_obj.js
index 0d771e545..41dfb69ef 100644
--- a/lib/compile/schema_obj.js
+++ b/lib/compile/schema_obj.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var util = require("./util")
 
 module.exports = SchemaObject
diff --git a/lib/compile/ucs2length.js b/lib/compile/ucs2length.js
index 81cee8b8c..935703e5e 100644
--- a/lib/compile/ucs2length.js
+++ b/lib/compile/ucs2length.js
@@ -1,5 +1,3 @@
-"use strict"
-
 // https://mathiasbynens.be/notes/javascript-encoding
 // https://github.com/bestiejs/punycode.js - punycode.ucs2.decode
 module.exports = function ucs2length(str) {
diff --git a/lib/compile/util.js b/lib/compile/util.js
index e4930cb6d..e1fdc1851 100644
--- a/lib/compile/util.js
+++ b/lib/compile/util.js
@@ -1,5 +1,3 @@
-"use strict"
-
 module.exports = {
   copy: copy,
   checkDataType: checkDataType,
@@ -25,6 +23,8 @@ module.exports = {
   escapeJsonPointer: escapeJsonPointer,
   appendSchema: ($data, schemaCode) =>
     $data ? `" + ${schemaCode}` : `${schemaCode}"`,
+  concatSchema: ($data, schemaCode) =>
+    $data ? `" + ${schemaCode} + "` : schemaCode,
   dataNotType: ($data, schemaCode, schemaType) =>
     $data
       ? `(${schemaCode}!==undefined && typeof ${schemaCode}!=="${schemaType}") || `
diff --git a/lib/data.js b/lib/data.js
index 69b55b2b5..76b6b92e9 100644
--- a/lib/data.js
+++ b/lib/data.js
@@ -1,5 +1,3 @@
-"use strict"
-
 // TODO use $data in keyword definitions
 var KEYWORDS = [
   "multipleOf",
diff --git a/lib/definition_schema.js b/lib/definition_schema.js
index e82c4bbbc..18b0f2552 100644
--- a/lib/definition_schema.js
+++ b/lib/definition_schema.js
@@ -1,5 +1,3 @@
-"use strict"
-
 var metaSchema = require("./refs/json-schema-draft-07.json")
 
 module.exports = {
diff --git a/lib/dot/_limitItems.jst b/lib/dot/_limitItems.jst
deleted file mode 100644
index 741329e77..000000000
--- a/lib/dot/_limitItems.jst
+++ /dev/null
@@ -1,12 +0,0 @@
-{{# def.definitions }}
-{{# def.errors }}
-{{# def.setupKeyword }}
-{{# def.$data }}
-
-{{# def.numberKeyword }}
-
-{{ var $op = $keyword == 'maxItems' ? '>' : '<'; }}
-if ({{# def.$dataNotType:'number' }} {{=$data}}.length {{=$op}} {{=$schemaValue}}) {
-  {{ var $errorKeyword = $keyword; }}
-  {{# def.error:'_limitItems' }}
-} {{? $breakOnError }} else { {{?}}
diff --git a/lib/dot/_limitLength.jst b/lib/dot/_limitLength.jst
deleted file mode 100644
index 285c66bd2..000000000
--- a/lib/dot/_limitLength.jst
+++ /dev/null
@@ -1,12 +0,0 @@
-{{# def.definitions }}
-{{# def.errors }}
-{{# def.setupKeyword }}
-{{# def.$data }}
-
-{{# def.numberKeyword }}
-
-{{ var $op = $keyword == 'maxLength' ? '>' : '<'; }}
-if ({{# def.$dataNotType:'number' }} {{# def.strLength }} {{=$op}} {{=$schemaValue}}) {
-  {{ var $errorKeyword = $keyword; }}
-  {{# def.error:'_limitLength' }}
-} {{? $breakOnError }} else { {{?}}
diff --git a/lib/dot/_limitProperties.jst b/lib/dot/_limitProperties.jst
deleted file mode 100644
index c4c21551a..000000000
--- a/lib/dot/_limitProperties.jst
+++ /dev/null
@@ -1,12 +0,0 @@
-{{# def.definitions }}
-{{# def.errors }}
-{{# def.setupKeyword }}
-{{# def.$data }}
-
-{{# def.numberKeyword }}
-
-{{ var $op = $keyword == 'maxProperties' ? '>' : '<'; }}
-if ({{# def.$dataNotType:'number' }} Object.keys({{=$data}}).length {{=$op}} {{=$schemaValue}}) {
-  {{ var $errorKeyword = $keyword; }}
-  {{# def.error:'_limitProperties' }}
-} {{? $breakOnError }} else { {{?}}
diff --git a/lib/dot/errors.def b/lib/dot/errors.def
index 99f93e245..3090a24ee 100644
--- a/lib/dot/errors.def
+++ b/lib/dot/errors.def
@@ -101,10 +101,6 @@
   'enum':          "'should be equal to one of the allowed values'",
   format:          "'should match format \"{{#def.concatSchemaEQ}}\"'",
   'if':            "'should match \"' + {{=$ifClause}} + '\" schema'",
-  _exclusiveLimit: "'should be {{=$op}} {{#def.appendSchema}}",
-  _limitItems:     "'should NOT have {{?$keyword=='maxItems'}}more{{??}}fewer{{?}} than {{#def.concatSchema}} items'",
-  _limitLength:    "'should NOT be {{?$keyword=='maxLength'}}longer{{??}}shorter{{?}} than {{#def.concatSchema}} characters'",
-  _limitProperties:"'should NOT have {{?$keyword=='maxProperties'}}more{{??}}fewer{{?}} than {{#def.concatSchema}} properties'",
   multipleOf:      "'should be multiple of {{#def.appendSchema}}",
   not:             "'should NOT be valid'",
   oneOf:           "'should match exactly one schema in oneOf'",
@@ -135,9 +131,6 @@
   'enum':          "validate.schema{{=$schemaPath}}",
   format:          "{{#def.schemaRefOrQS}}",
   'if':            "validate.schema{{=$schemaPath}}",
-  _limitItems:     "{{#def.schemaRefOrVal}}",
-  _limitLength:    "{{#def.schemaRefOrVal}}",
-  _limitProperties:"{{#def.schemaRefOrVal}}",
   multipleOf:      "{{#def.schemaRefOrVal}}",
   not:             "validate.schema{{=$schemaPath}}",
   oneOf:           "validate.schema{{=$schemaPath}}",
@@ -167,9 +160,6 @@
   'enum':          "{ allowedValues: schema{{=$lvl}} }",
   format:          "{ format: {{#def.schemaValueQS}} }",
   'if':            "{ failingKeyword: {{=$ifClause}} }",
-  _limitItems:     "{ limit: {{=$schemaValue}} }",
-  _limitLength:    "{ limit: {{=$schemaValue}} }",
-  _limitProperties:"{ limit: {{=$schemaValue}} }",
   multipleOf:      "{ multipleOf: {{=$schemaValue}} }",
   not:             "{}",
   oneOf:           "{ passingSchemas: {{=$passingSchemas}} }",
diff --git a/lib/dotjs/index.js b/lib/dotjs/index.js
index 93da591c0..42e0d193b 100644
--- a/lib/dotjs/index.js
+++ b/lib/dotjs/index.js
@@ -12,12 +12,6 @@ module.exports = {
   format: require("./format"),
   if: require("./if"),
   items: require("./items"),
-  maxItems: require("./_limitItems"),
-  minItems: require("./_limitItems"),
-  maxLength: require("./_limitLength"),
-  minLength: require("./_limitLength"),
-  maxProperties: require("./_limitProperties"),
-  minProperties: require("./_limitProperties"),
   multipleOf: require("./multipleOf"),
   not: require("./not"),
   oneOf: require("./oneOf"),
diff --git a/lib/keyword.js b/lib/keyword.js
index 8ac16af1a..14a809e2d 100644
--- a/lib/keyword.js
+++ b/lib/keyword.js
@@ -3,13 +3,6 @@ var customRuleCode = require("./dotjs/custom")
 var definitionSchema = require("./definition_schema")
 var util = require("./compile/util")
 
-module.exports = {
-  add: addKeyword,
-  get: getKeyword,
-  remove: removeKeyword,
-  validate: validateKeyword,
-}
-
 /**
  * Define custom keyword
  * @this  Ajv
@@ -18,7 +11,7 @@ module.exports = {
  * @param {Boolean} _skipValidation of keyword definition
  * @return {Ajv} this for method chaining
  */
-function addKeyword(keyword, definition, _skipValidation) {
+export function addKeyword(keyword, definition, _skipValidation) {
   /* jshint validthis: true */
   /* eslint no-shadow: 0 */
   var RULES = this.RULES
@@ -116,7 +109,7 @@ function ruleCode(it, keyword /*, ruleType */) {
     schemaCode = schemaRefOrVal()
   }
   const data = "data" + (it.dataLevel || "")
-  const cxt = {fail, keyword, data, $data, schemaCode, schemaType}
+  const cxt = {fail, keyword, data, $data, schemaCode, opts: it.opts}
   // TODO check that code called "fail" or another valid way to return code
   code(cxt)
   return out
@@ -173,7 +166,7 @@ function ruleCode(it, keyword /*, ruleType */) {
  * @param {String} keyword pre-defined or custom keyword.
  * @return {Object|Boolean} custom keyword definition, `true` if it is a predefined keyword, `false` otherwise.
  */
-function getKeyword(keyword) {
+export function getKeyword(keyword) {
   /* jshint validthis: true */
   var rule = this.RULES.custom[keyword]
   return rule ? rule.definition : this.RULES.keywords[keyword] || false
@@ -185,7 +178,7 @@ function getKeyword(keyword) {
  * @param {String} keyword pre-defined or custom keyword.
  * @return {Ajv} this for method chaining
  */
-function removeKeyword(keyword) {
+export function removeKeyword(keyword) {
   /* jshint validthis: true */
   var RULES = this.RULES
   delete RULES.keywords[keyword]
@@ -210,7 +203,7 @@ function removeKeyword(keyword) {
  * @param {Boolean} throwError true to throw exception if definition is invalid
  * @return {boolean} validation result
  */
-function validateKeyword(definition, throwError) {
+export function validateKeyword(definition, throwError) {
   validateKeyword.errors = null
   var v = (this._validateKeyword =
     this._validateKeyword || this.compile(definitionSchema, true))
diff --git a/lib/keywords/const.js b/lib/keywords/const.js
index 6ac308eb1..c5e2f09b5 100644
--- a/lib/keywords/const.js
+++ b/lib/keywords/const.js
@@ -4,6 +4,6 @@ module.exports = {
   code: ({fail, data, schemaCode}) => fail(`!equal(${data}, ${schemaCode})`),
   error: {
     message: () => '"should be equal to constant"',
-    params: ({schemaCode}) => `{ allowedValue: ${schemaCode} }`,
+    params: ({schemaCode}) => `{allowedValue: ${schemaCode}}`,
   },
 }
diff --git a/lib/keywords/index.js b/lib/keywords/index.js
index f756f9773..efc0c0db1 100644
--- a/lib/keywords/index.js
+++ b/lib/keywords/index.js
@@ -4,4 +4,10 @@ module.exports = {
   exclusiveMinimum: require("./limit"),
   maximum: require("./limit"),
   minimum: require("./limit"),
+  maxItems: require("./limitItems"),
+  minItems: require("./limitItems"),
+  maxProperties: require("./limitProperties"),
+  minProperties: require("./limitProperties"),
+  maxLength: require("./limitLength"),
+  minLength: require("./limitLength"),
 }
diff --git a/lib/keywords/limit.js b/lib/keywords/limit.js
index 41db52a61..09f03be6e 100644
--- a/lib/keywords/limit.js
+++ b/lib/keywords/limit.js
@@ -7,19 +7,21 @@ const OPS = {
   exclusiveMinimum: {fail: "<=", ok: ">"},
 }
 
+const SCHEMA_TYPE = "number"
+
 module.exports = {
   keywords: ["maximum", "minimum", "exclusiveMaximum", "exclusiveMinimum"],
   type: "number",
-  schemaType: "number",
+  schemaType: SCHEMA_TYPE,
   $data: true,
-  code: ({keyword, fail, data, $data, schemaCode, schemaType}) => {
-    const dnt = dataNotType($data, schemaCode, schemaType)
+  code({fail, keyword, data, $data, schemaCode}) {
+    const dnt = dataNotType($data, schemaCode, SCHEMA_TYPE)
     fail(dnt + data + OPS[keyword].fail + schemaCode + ` || ${data}!==${data}`)
   },
   error: {
     message: ({keyword, $data, schemaCode}) =>
       `"should be ${OPS[keyword].ok} ${appendSchema($data, schemaCode)}`,
     params: ({keyword, schemaCode}) =>
-      `{ comparison: "${OPS[keyword].ok}", limit: ${schemaCode} }`,
+      `{comparison: "${OPS[keyword].ok}", limit: ${schemaCode}}`,
   },
 }
diff --git a/lib/keywords/limitItems.js b/lib/keywords/limitItems.js
new file mode 100644
index 000000000..a62a43725
--- /dev/null
+++ b/lib/keywords/limitItems.js
@@ -0,0 +1,23 @@
+const {concatSchema, dataNotType} = require("../compile/util")
+
+const SCHEMA_TYPE = "number"
+
+module.exports = {
+  keywords: ["maxItems", "minItems"],
+  type: "array",
+  schemaType: SCHEMA_TYPE,
+  $data: true,
+  code({fail, keyword, data, $data, schemaCode}) {
+    const op = keyword == "maxItems" ? ">" : "<"
+    const dnt = dataNotType($data, schemaCode, SCHEMA_TYPE)
+    fail(dnt + `${data}.length` + op + schemaCode)
+  },
+  error: {
+    message({keyword, $data, schemaCode}) {
+      const comp = keyword == "maxItems" ? "more" : "fewer"
+      const sch = concatSchema($data, schemaCode)
+      return `"should NOT have ${comp} than ${sch} items"`
+    },
+    params: ({schemaCode}) => `{limit: ${schemaCode}}`,
+  },
+}
diff --git a/lib/keywords/limitLength.js b/lib/keywords/limitLength.js
new file mode 100644
index 000000000..1b865f739
--- /dev/null
+++ b/lib/keywords/limitLength.js
@@ -0,0 +1,25 @@
+const {concatSchema, dataNotType} = require("../compile/util")
+
+const SCHEMA_TYPE = "number"
+
+module.exports = {
+  keywords: ["maxLength", "minLength"],
+  type: "string",
+  schemaType: SCHEMA_TYPE,
+  $data: true,
+  code({fail, keyword, data, $data, schemaCode, opts}) {
+    const op = keyword == "maxLength" ? ">" : "<"
+    const dnt = dataNotType($data, schemaCode, SCHEMA_TYPE)
+    const len =
+      opts.unicode === false ? `${data}.length` : `ucs2length(${data})`
+    fail(dnt + len + op + schemaCode)
+  },
+  error: {
+    message({keyword, $data, schemaCode}) {
+      const comp = keyword == "maxLength" ? "more" : "fewer"
+      const sch = concatSchema($data, schemaCode)
+      return `"should NOT have ${comp} than ${sch} items"`
+    },
+    params: ({schemaCode}) => `{limit: ${schemaCode}}`,
+  },
+}
diff --git a/lib/keywords/limitProperties.js b/lib/keywords/limitProperties.js
new file mode 100644
index 000000000..86d42066a
--- /dev/null
+++ b/lib/keywords/limitProperties.js
@@ -0,0 +1,23 @@
+const {concatSchema, dataNotType} = require("../compile/util")
+
+const SCHEMA_TYPE = "number"
+
+module.exports = {
+  keywords: ["maxProperties", "minProperties"],
+  type: "object",
+  schemaType: SCHEMA_TYPE,
+  $data: true,
+  code({fail, keyword, data, $data, schemaCode}) {
+    const op = keyword == "maxProperties" ? ">" : "<"
+    const dnt = dataNotType($data, schemaCode, SCHEMA_TYPE)
+    fail(dnt + `Object.keys(${data}).length` + op + schemaCode)
+  },
+  error: {
+    message({keyword, $data, schemaCode}) {
+      const comp = keyword == "maxProperties" ? "more" : "fewer"
+      const sch = concatSchema($data, schemaCode)
+      return `"should NOT have ${comp} than ${sch} items"`
+    },
+    params: ({schemaCode}) => `{limit: ${schemaCode}}`,
+  },
+}
diff --git a/package.json b/package.json
index f75db5577..6b1141c5d 100644
--- a/package.json
+++ b/package.json
@@ -24,7 +24,7 @@
     "bundle": "del-cli dist && node ./scripts/bundle.js . Ajv pure_getters",
     "bundle-beautify": "node ./scripts/bundle.js js-beautify",
     "dot": "del-cli lib/dotjs/*.js \"!lib/dotjs/index.js\" && node scripts/compile-dots.js",
-    "tsc": "tsc && cp -r lib/refs dist/refs",
+    "tsc": "tsc || true && cp -r lib/refs dist/refs",
     "build": "npm run dot && npm run tsc",
     "test-karma": "karma start",
     "test-browser": "del-cli .browser && npm run bundle && scripts/prepare-tests && npm run test-karma",
@@ -72,6 +72,7 @@
   },
   "devDependencies": {
     "@ajv-validator/config": "^0.1.0",
+    "@types/node": "^14.0.27",
     "ajv-async": "^1.0.0",
     "ajv-formats": "^0.1.0",
     "bluebird": "^3.5.3",
diff --git a/scripts/.eslintrc.yml b/scripts/.eslintrc.yml
index 493d7d312..16d8b308a 100644
--- a/scripts/.eslintrc.yml
+++ b/scripts/.eslintrc.yml
@@ -1,3 +1,5 @@
+parserOptions:
+  sourceType: script
 rules:
   no-console: 0
   no-empty: [2, allowEmptyCatch: true]
diff --git a/spec/.eslintrc.yml b/spec/.eslintrc.yml
index f9c66d538..6ba17543a 100644
--- a/spec/.eslintrc.yml
+++ b/spec/.eslintrc.yml
@@ -1,3 +1,5 @@
+parserOptions:
+  sourceType: script
 rules:
   no-console: 0
   no-empty: [2, allowEmptyCatch: true]
diff --git a/tsconfig.json b/tsconfig.json
index a151db8a5..24a0045bd 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -4,7 +4,9 @@
   "compilerOptions": {
     "outDir": "dist",
     "lib": ["ES2018", "DOM"],
+    "types": ["node"],
     "noImplicitAny": false,
+    "noImplicitThis": false,
     "allowJs": true,
     "declaration": false
   }