每日一题 - 2019-11-25 - 写一个debounce的装饰器 ​

/**
 * 装饰器的debounce
 * @param delay
 */
export function debounce(delay: number): Function {
  return (
    target: Function,
    propertyKey: string,
    propertyDesciptor: PropertyDescriptor
  ) => {
    const method = propertyDesciptor.value;
    let timer = null;
    propertyDesciptor.value = (...args) => {
      if (timer) {
        clearTimeout(timer);
        timer = null;
      }
      timer = setTimeout(() => method(...args), delay);
    };
    return propertyDesciptor;
  };
}

/**
 * 装饰器的debounce
 * @param delay
 */
export function debounce(delay: number): Function {
  return (
    target: Function,
    propertyKey: string,
    propertyDesciptor: PropertyDescriptor
  ) => {
    const method = propertyDesciptor.value;
    let timer = null;
    propertyDesciptor.value = (...args) => {
      if (timer) {
        clearTimeout(timer);
        timer = null;
      }
      timer = setTimeout(() => method(...args), delay);
    };
    return propertyDesciptor;
  };
}

import { debounce } from './index';

jest.useFakeTimers();

let a: any;
let mockFunc: jest.Mock;
beforeEach(() => {
  mockFunc = jest.fn();
  class Test {
    @debounce(1000)
    sayHi() {
      mockFunc();
    }
  }
  a = new Test();
});

describe('debounce:', () => {
  test('debounced function should be called after the delay time', () => {
    a.sayHi();
    expect(mockFunc).toHaveBeenCalledTimes(0);
    jest.advanceTimersByTime(1000);
    expect(mockFunc).toHaveBeenCalledTimes(1);
  });

  test('debounced function should not be called before the delay time', () => {
    a.sayHi();
    expect(mockFunc).toHaveBeenCalledTimes(0);
    let count = 100;
    while (count--) {
      a.sayHi();
    }
    expect(mockFunc).toHaveBeenCalledTimes(0);

    count = 100;
    while (count--) {
      jest.advanceTimersByTime(999);
      a.sayHi();
    }
    expect(mockFunc).toHaveBeenCalledTimes(0);
  });
});

import { debounce } from './index';

jest.useFakeTimers();

let a: any;
let mockFunc: jest.Mock;
beforeEach(() => {
  mockFunc = jest.fn();
  class Test {
    @debounce(1000)
    sayHi() {
      mockFunc();
    }
  }
  a = new Test();
});

describe('debounce:', () => {
  test('debounced function should be called after the delay time', () => {
    a.sayHi();
    expect(mockFunc).toHaveBeenCalledTimes(0);
    jest.advanceTimersByTime(1000);
    expect(mockFunc).toHaveBeenCalledTimes(1);
  });

  test('debounced function should not be called before the delay time', () => {
    a.sayHi();
    expect(mockFunc).toHaveBeenCalledTimes(0);
    let count = 100;
    while (count--) {
      a.sayHi();
    }
    expect(mockFunc).toHaveBeenCalledTimes(0);

    count = 100;
    while (count--) {
      jest.advanceTimersByTime(999);
      a.sayHi();
    }
    expect(mockFunc).toHaveBeenCalledTimes(0);
  });
});