contextBridge

Create a safe, bi-directional, synchronous bridge across isolated contexts

进程: 渲染进程

An example of exposing an API to a renderer from an isolated preload script is given below:

// Preload (Isolated World)
const { contextBridge, ipcRenderer } = require('electron')
contextBridge.exposeInMainWorld(
  'electron',
  {
    doThing: () => ipcRenderer.send('do-a-thing')
  }
)

// Renderer (Main World)
window.electron.doThing()

词汇表

Main World

The “Main World” is the JavaScript context that your main renderer code runs in. By default, the page you load in your renderer executes code in this world.

Isolated World

When contextIsolation is enabled in your webPreferences, your preload scripts run in an “Isolated World”. You can read more about context isolation and what it affects in the security docs.

方法

The contextBridge module has the following methods:

contextBridge.exposeInMainWorld(apiKey, api) Experimental

• apiKey String - The key to inject the API onto window with. The API will be accessible on window[apiKey].
• api Record - Your API object, more information on what this API can be and how it works is available below.

用法

API Objects

The api object provided to exposeInMainWorld must be an object whose keys are strings and values are a Function, String, Number, Array, Boolean, or another nested object that meets the same conditions.

Function values are proxied to the other context and all other values are copied and frozen. Any data / primitives sent in the API object become immutable and updates on either side of the bridge do not result in an update on the other side.

An example of a complex API object is shown below:

const { contextBridge } = require('electron')
contextBridge.exposeInMainWorld(
  'electron',
  {
    doThing: () => ipcRenderer.send('do-a-thing'),
    myPromises: [Promise.resolve(), Promise.reject(new Error('whoops'))],
    anAsyncFunction: async () => 123,
    data: {
      myFlags: ['a', 'b', 'c'],
      bootTime: 1234
    },
    nestedAPI: {
      evenDeeper: {
        youCanDoThisAsMuchAsYouWant: {
          fn: () => ({
            returnData: 123
          })
        }
      }
    }
  }
)

API Functions

Function values that you bind through the contextBridge are proxied through Electron to ensure that contexts remain isolated. This results in some key limitations that we’ve outlined below.

Parameter / Error / Return Type support

Because parameters, errors and return values are copied when they are sent over the bridge, there are only certain types that can be used. At a high level, if the type you want to use can be serialized and deserialized into the same object it will work. A table of type support has been included below for completeness:

If the type you care about is not in the above table, it is probably not supported.