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faq.md

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FAQ

Command errors in Windows

Please install Git for Windows first, see For Windows for more information.

Gradle errors in Android Studio

Downloading license-gradle-plugin.jar may trigger errors, like Connection reset or peer not authenticated. Maybe a network problem, try a proxy or VPN.

Use local image

Weex's native runtime support load image file from device's disk, all you have to do set the file url like file:///sdcard/image_new0.png. As to load image file in your project, Weex is not support yet.

Error（The header content contains invalid characters) in windows

This's is caused by weex-toolkit's dependency 'http-server', whose old version is not working well in chinese windows environment. We have fixed that, you should upgrade weex-toolkit before use that.

Playground app display nothing (white screen) after scan

Best way to find out what's happening is read debug log, you can follow this document to firgure out how to do that.

About ECMAScript Version

Weex uses JSCore in iOS and uses v8 in Android. So they both support ECMAScript 5 spec. Additionally, we do some polyfills in native environment:

  • Promise in iOS/Android
  • Timer APIs (setTimeout/clearTimeout/setInterval/clearInterval) in iOS/Android
  • console in iOS/Android

In Browser we contains a polyfill of Promise temporarily. In the future developers can choose whether to import a polyfill by configurations.

You can also write ES6 syntax by babel with webpack. The loader will convert ES6 syntax into ES5 automatically.

If you want more ES6 polyfills you can import them into the JS Bundle as you like.

Dependencies in frontend

In Weex you may have some ways to import/require a component or a JS module. Take ES5 syntax for example:

  • require('xxx.js'): depends on a JS file
  • require('npm-module-name'): depends on a NPM module
  • require('xxx.we'): include a we file to register a Weex custom component
  • require('@weex-module/xxx'): depends on a Weex native module. Notice that it is supported only in *.we file not *.js file. If you want to use Weex native module in a *.js file, temporarily you may write like this:
// use this piece of code below to get Weex native module "modal"
var modal
__weex_define__('@weex-temp/x', function (__weex_require__) {
  modal = __weex_require__('@weex-module/modal')
})

// use APIs in "modal" module
modal.toast({message: 'hello'})

We will bring a better syntax design in the future.

How to detect an native module/component supported in JavaScript?

Detect native module

var xxx = require('@weex-module/xxx')
if (xxx) {
  // todo: use this module
}
else {
  // todo: handle the exception
}

Detect native component

<template>
  <component is="{{type}}"></component>
</template>

<script>
  var type = 'xxx'
  var xxx = require('@weex-component/xxx')
  if (!xxx) {
    type = 'div' // downgrade to <div>
  }
  module.exports = {
    data: function () {
      return {
        type: type
      }
    }
  }
</script>

Transfer data between pages

If you have 2 pages, A and B.

  1. A -> B, use getConfig api or storage module to transfer data
  2. B -> A, use storage module to transfer data