Use and test linter for ts

.travis.yml

@@ -15,6 +15,7 @@ install:
   - conda install --yes $DEPS
   - python setup.py install
   - jupyter nbextension install vega --py --sys-prefix
+  - yarn
 
 before_install:
   - wget https://repo.continuum.io/miniconda/Miniconda3-latest-Linux-x86_64.sh -O miniconda.sh
@@ -24,4 +25,5 @@ before_install:
   - conda update --yes conda
 
 script:
+  - yarn lint
   - py.test vega

package.json

@@ -13,6 +13,8 @@
   },
   "homepage": "https://github.com/vega/ipyvega#readme",
   "scripts": {
+    "format": "prettier --write 'src/*.ts'",
+    "lint": "prettier --list-different 'src/*.ts'",
     "build": "webpack --mode production",
     "watch": "webpack --mode development --watch"
   },
@@ -21,6 +23,7 @@
   },
   "devDependencies": {
     "css-loader": "^0.28.11",
+    "prettier": "^1.13.7",
     "ts-loader": "^4.4.1",
     "typescript": "^2.9.1",
     "webpack": "^4.12.0",

src/index.ts

@@ -2,7 +2,7 @@ import vegaEmbed, { Mode, EmbedOptions } from "vega-embed";
 import { Spec } from "vega-lib";
 import { TopLevelSpec } from "vega-lite";
 
-export { default as vegaEmbed } from 'vega-embed';
+export { default as vegaEmbed } from "vega-embed";
 
 function javascriptIndex(selector: string, outputs) {
   // Return the index in the output array of the JS repr of this viz

yarn.lock

@@ -2469,6 +2469,10 @@ prepend-http@^1.0.0:
   version "1.0.4"
   resolved "https://registry.yarnpkg.com/prepend-http/-/prepend-http-1.0.4.tgz#d4f4562b0ce3696e41ac52d0e002e57a635dc6dc"
 
+prettier@^1.13.7:
+  version "1.13.7"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.13.7.tgz#850f3b8af784a49a6ea2d2eaa7ed1428a34b7281"
+
 process-nextick-args@~2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/process-nextick-args/-/process-nextick-args-2.0.0.tgz#a37d732f4271b4ab1ad070d35508e8290788ffaa"