feat: add support for webContents.executeJavaScript (#366)

* webContents.executeJavaScript now works as intended

* Document difference with webContents.executeJavaScript between spectron and electron

* tests for webContents.executeJavaScript

* fix lint error

* var to const

README.md

@@ -305,6 +305,18 @@ app.webContents.savePage('/Users/kevin/page.html', 'HTMLComplete')
   })
 ```
 
+##### executeJavaScript
+The async `executeJavaScript` API is supported but instead of taking a callback it
+returns a `Promise` that will resolve with the result of the last statement of the
+script.
+
+```js
+app.webContents.executeJavaScript('1 + 2')
+  .then(function (result) {
+    console.log(result) // prints 3
+  })
+```
+
 #### mainProcess
 
 The `mainProcess` property is an alias for `require('electron').remote.process`.

lib/api.js

@@ -342,7 +342,8 @@ Api.prototype.addWebContentsApis = function (api) {
   app.webContents = {}
 
   const asyncApis = {
-    'webContents.savePage': true
+    'webContents.savePage': true,
+    'webContents.executeJavaScript': true
   }
 
   Object.keys(api).filter(function (name) {
@@ -361,6 +362,7 @@ Api.prototype.addWebContentsApis = function (api) {
   })
 
   this.addSavePageSupport()
+  this.addExecuteJavaScriptSupport()
 }
 
 Api.prototype.addSavePageSupport = function () {
@@ -385,6 +387,22 @@ Api.prototype.addSavePageSupport = function () {
   }
 }
 
+Api.prototype.addExecuteJavaScriptSupport = function () {
+  const app = this.app
+  const self = this
+
+  app.client.addCommand('webContents.executeJavaScript', function (code, useGesture) {
+    return this.executeAsync(function (code, useGesture, requireName, done) {
+      const webContents = window[requireName]('electron').remote.getCurrentWebContents()
+      webContents.executeJavaScript(code, useGesture, done)
+    }, code, useGesture, self.requireName).then(getResponseValue)
+  })
+
+  app.webContents.executeJavaScript = function () {
+    return app.client['webContents.executeJavaScript'].apply(app.client, arguments)
+  }
+}
+
 Api.prototype.addProcessApis = function (api) {
   var app = this.app
   app.rendererProcess = {}

lib/spectron.d.ts

@@ -58,6 +58,7 @@ declare module "spectron" {
         ):boolean;
         savePage(fullPath:string, saveType:"HTMLOnly" | "HTMLComplete" | "MHTML"):Promise<void>;
         savePage(fullPath:string, saveType:"HTMLOnly" | "HTMLComplete" | "MHTML"):any;
+        executeJavaScript(code:string, userGesture?:boolean):Promise<any>;
     }
 
     type BasicAppSettings = {

test/application-test.js

@@ -228,6 +228,26 @@ describe('application loading', function () {
     })
   })
 
+  describe('webContents.executeJavaScript', function () {
+    it('executes the given script and returns the result of its last statement (sync)', function () {
+      return app.webContents.executeJavaScript('1 + 2').then(function (result) {
+        expect(result).to.equal(3)
+      })
+    })
+
+    it('executes the given script and returns the result of its last statement (async)', function () {
+      return app.webContents.executeJavaScript(`
+        new Promise(function(resolve){
+          setTimeout(function(){
+            resolve("ok")
+          }, 1000)
+        })`
+      ).then(function (result) {
+        expect(result).to.equal('ok')
+      })
+    })
+  })
+
   describe('electron.ipcRenderer.send', function () {
     it('sends the message to the main process', function () {
       return app.electron.remote.getGlobal('ipcEventCount').should.eventually.equal(0)