add support for webpack4 (#138)

README.md

@@ -173,7 +173,7 @@ module.exports = {
 }
 ```
 
-### `importSripts` usage example
+### `importScripts` usage example
 
 Accepts an array of `<String|Object>`'s. `String` entries are legacy supported. Use `filename` instead.
 
@@ -213,7 +213,7 @@ plugins: [
       // import(/* webpackChunkName: "my-named-chunk" */ './my-async-script.js');
       { chunkName: 'my-named-chunk' },
 
-      // All importSripts entries resolve to a string, therefore
+      // All importScripts entries resolve to a string, therefore
       // the final output of the above input is:
       // [
       //   '/my/public/path/some-known-script-path.js',

package.json

@@ -45,7 +45,7 @@
     "test": "./test"
   },
   "peerDependencies": {
-    "webpack": "^1 || ^2 || ^2.1.0-beta || ^2.2.0-beta || ^3"
+    "webpack": "^1 || ^2 || ^2.1.0-beta || ^2.2.0-beta || ^3 || ^4"
   },
   "dependencies": {
     "del": "^2.2.2",

src/index.js

@@ -68,7 +68,7 @@ class SWPrecacheWebpackPlugin {
 
   apply(compiler) {
     // sw-precache needs physical files to reference so we MUST wait until after assets are emitted before generating the service-worker.
-    compiler.plugin('after-emit', (compilation, callback) => {
+    const afterEmit = (compilation, callback = () => {}) => {
       this.configure(compiler, compilation);  // configure the serviceworker options
       this.checkWarnings(compilation);
 
@@ -77,7 +77,12 @@ class SWPrecacheWebpackPlugin {
         .then(serviceWorker => this.writeServiceWorker(serviceWorker, compiler))
         .then(() => callback())
         .catch(err => callback(err));
-    });
+    };
+    if (compiler.hooks) {
+      compiler.hooks.afterEmit.tap('swPrecache', afterEmit);
+    } else {
+      compiler.plugin('after-emit', afterEmit);
+    }
   }
 
   configure(compiler, compilation) {