harmony 鸿蒙JavaScript

2023-06-24
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JavaScript

You can use a .js file in the ECMAScript compliant JavaScript language to define the service logic of an HML page. With dynamic typing, JavaScript can make your application more expressive with a flexible design. The following describes the JavaScript compilation and running.

Syntax

The ECMAScript 6.0 syntax is supported. Lite wearables only support the following ECMAScript 6.0 syntax:

let/const
arrow functions
class
default value
destructuring assignment
destructuring binding pattern
enhanced object initializer
for-of
rest parameter
template strings
Module declaration Import functionality modules.

  import router from '@ohos.router';

Code reference Import JavaScript code.

  import utils from '../../common/utils.js';

Objects

Page objects |Attribute |Type |Description | |—–|—————|—————————————-| |data|Object/Function|Data model of the page. If the attribute is of the function type, the return value must be of the object type. The name cannot start with a dollar sign ($) or underscore (_). Do not use reserved words (for, if, show, and tid).
| |$refs|Object |DOM elements or child component instances that have registered the ref attribute. For an example, see Obtaining a DOM Element.|

Obtaining a DOM Element

Use $refs to obtain a DOM element.

<!-- index.hml -->
<div class="container">
  <image-animator class="image-player" ref="animator" images="{{images}}" duration="1s" onclick="handleClick"></image-animator>
</div>

   // index.js
   export default {
     data: {
       images: [
         { src: '/common/frame1.png' },
         { src: '/common/frame2.png' },
         { src: '/common/frame3.png' },
       ],
     },
     handleClick() {
       const animator = this.$refs.animator; // Obtain the DOM element whose $refs attribute is animator.
       const state = animator.getState();
       if (state === 'paused') {
         animator.resume();
       } else if (state === 'stopped') {
         animator.start();
       } else {
         animator.pause();
       }
     },
   };

Lifecycle APIs

Page lifecycle APIs |Name |Type |Parameter|Return Value|Description |Triggered When | |———|——–|—-|—-|——|——————-| |onInit |Function|N/A |N/A |Listens for page initialization.|Page initialization is complete. This API is called only once in the page lifecycle.| |onReady |Function|N/A |N/A |Listens for page creation.|A page is created. This API is called only once in the page lifecycle. | |onShow |Function|N/A |N/A |Listens for page display.|The page is displayed. | |onHide |Function|N/A |N/A |Listens for page disappearance.|The page disappears. | |onDestroy|Function|N/A |N/A |Listens for page destruction.|The page is destroyed. |

The lifecycle APIs of page A are called in the following sequence:
- Open page A: onInit() -> onReady() -> onShow()
- Open page B on page A: onHide() -> onDestroy()
- Go back to page A from page B: onInit() -> onReady() -> onShow()
- Exit page A: onHide() -> onDestroy()
- Hide page A: onHide()
- Show background page A on the foreground: onShow()
Application lifecycle APIs |Name |Type |Parameter|Return Value|Description|Triggered When | |———|——–|—-|—-|—-|———| |onCreate|Function|N/A |N/A |Listens for application creation.|The application is created.| |onDestroy|Function|N/A |N/A |Listens for application exit.|The application exits.|