javascript - 如何访问 Chart.js 自定义工具提示界面中的类变量

Question

在单击事件的工具提示下的自定义工具提示中的以下代码片段中，当我尝试使用它时，类变量无法访问，它仅显示与 ChartElement 相关的值

@Output() valuechange = new EventEmitter<any>();
options: ChartOptions = {
responsive: true,
maintainAspectRatio: false,
tooltips: {
  displayColors: false,
  mode: 'nearest',
  intersect: false,
  enabled: false,
  custom(tooltipModel: any) {
    // tooltip element
    let tooltipEl: any = document.querySelector('#chartjs-tooltip');

    // create element on first render
    if (!tooltipEl) {
      tooltipEl = document.createElement('div');
      tooltipEl.id = 'chartjs-tooltip';
      tooltipEl.style.width = '124px';
      tooltipEl.style.color = 'white';
      tooltipEl.style.borderRadius = '6px';
      tooltipEl.style.backgroundColor = 'rgba(55, 71, 79, 0.8)';
      tooltipEl.innerHTML = '<div style ="display:flex;flex-direction:column">sample tooltip</div>';
      document.body.appendChild(tooltipEl);
    }

      tooltipEl.onclick = () => {
        // NOT ABLE TO Access this to emit event 
        // this.valuechange.emit('test');
        console.log('hi); // working
      };
    }
}

Answer 1

要使 this 等于该类，请将其编写为箭头函数:

custom: () => {
 console.log(this); // should be the class
}

但有时您需要 this 和 that 的句柄，其中 this 是类，that 是图表对象。

创建实用函数:

export const thisAsThat = (callBack: Function) => {
    const self = this;
    return function () {
      return callBack.apply(self, [this].concat(Array.prototype.slice.call(arguments)));
    };
  }

然后:

import { thisAsThat } from './where/thisAsThat/is/located';
....
custom: thisAsThat((that: any, otherArgument: any) => {
  console.log(this); // the class
  console.log(that); // the chart object
})

TypeScript: How to use both fat arrow and this?