Category: JavaScript Answers

Sometimes, we want to attach ‘onclick’ event to D3 chart background with JavaScript.

In this article, we’ll look at how to attach ‘onclick’ event to D3 chart background with JavaScript.

How to attach ‘onclick’ event to D3 chart background with JavaScript?

To attach ‘onclick’ event to D3 chart background with JavaScript, we call the on method.

For instance, we write

rect.on("click", () => {
  console.log("rect");
  d3.event.stopPropagation();
});

to call on with 'click to add a click listener to the rect object.

In the event listener, we call stopPropagation to stop the event from bubbling up.

Conclusion

To attach ‘onclick’ event to D3 chart background with JavaScript, we call the on method.

To change ISO date string to Date object with JavaScript, we use moment.js.

For instance, we write

const d = moment("2022-11-03T19:38:34.203Z", "YYYY-MM-DD HH:mm").toDate();

to call moment with the ISO date string and the date format to parse the date into a moment object that has the date in UTC.

Then we call toDate to convert it to a JavaScript date object.

Sometimes, we want to dispatch multiple actions in Redux and JavaScript.

In this article, we’ll look at how to dispatch multiple actions in Redux and JavaScript.

How to dispatch multiple actions in Redux and JavaScript?

To dispatch multiple actions in Redux and JavaScript, we call dispatch multiple times.

For instance, we write

const action1 = (id) => {
  return (dispatch) => {
    dispatch(action2(id));
    dispatch(action3(id));
  };
};

to call dispatch with all the actions we want to dispatch in the function returned by action1.

Conclusion

To dispatch multiple actions in Redux and JavaScript, we call dispatch multiple times.

Sometimes, we want to fix JavaScript error "val.match is not a function"

In this article, we’ll look at how to fix JavaScript error "val.match is not a function".

How to fix JavaScript error "val.match is not a function"?

To fix JavaScript error "val.match is not a function", we should make sure val is a string.

For instance, we write

const val = 12;

if (String(val).match(/^s+$/) || val === "") {
  console.log("success: ", val);
}

to call String with val to convert it to a string.

Then we call match on the returned string.

Conclusion

To fix JavaScript error "val.match is not a function", we should make sure val is a string.

Sometimes, we want to spy on function with Jest and JavaScript.

In this article, we’ll look at how to spy on function with Jest and JavaScript.

How to spy on function with Jest and JavaScript?

To spy on function with Jest and JavaScript, we use the spyOn method.

For instance, we write

import { mount } from "enzyme";

describe("My component", () => {
  it("should call getData", () => {
    const spy = jest.spyOn(Component.prototype, "getData");
    mount(<Component />);
    expect(spy).toHaveBeenCalledTimes(1);
  });
});

to call spyOn on the Component‘s getData instance method with spyOn.

Then we call mount to mount the Component.

And then we call toHaveBeenCalledTimes with 1 to check if getData has been called once.

Conclusion

To spy on function with Jest and JavaScript, we use the spyOn method.