HarmonyOS 获取当前一个字符串所占据的字节数，没有找到相关的API，请问如何实现？

import util from '@ohos.util';  
  
@Entry  
@Component  
struct Index {  
  @State message: string = 'Hello World';  
  
  build() {  
    Row() {  
      Column() {  
        Text(this.message)  
          .fontSize(50)  
          .fontWeight(FontWeight.Bold)  
          .onClick(() => {  
            let str = 'abcd哦#'  
            let that = new util.TextEncoder("utf-8");  
            let buffer = new ArrayBuffer(str.length * 5);  
            let dest = new Uint8Array(buffer);  
            let result = that.encodeIntoUint8Array(str, dest);  
            console.info('written: ' + result.written);  
            console.info('result: ' + JSON.stringify(result));  
          })  
      }  
      .width('100%')  
    }  
    .height('100%')  
  }  
}