Category: JavaScript

Sometimes, we want to check object equality in Jasmine and JavaScript.

In this article, we’ll look at how to check object equality in Jasmine and JavaScript.

How to check object equality in Jasmine and JavaScript?

To check object equality in Jasmine and JavaScript, we can use the toEqual method.

For instance, we write

describe("jasmine.objectContaining", () => {
  let foo;

  beforeEach(() => {
    foo = {
      a: 1,
      b: 2,
      bar: "baz",
    };
  });

  it("matches objects with the expect key/value pairs", () => {
    expect(foo).toEqual(
      jasmine.objectContaining({
        bar: "baz",
      })
    );
  });
});

to call toEqual in the it callback.

We call it with the value returned by jasmine.objectContaining which checks if the foo object has the properties we’re looking for.

Conclusion

To check object equality in Jasmine and JavaScript, we can use the toEqual method.

Sometimes, we want to check if a div does not exist with JavaScript.

In this article, we’ll look at how to check if a div does not exist with JavaScript.

How to check if a div does not exist with JavaScript?

To check if a div does not exist with JavaScript, we can check if null is returned when we try to select an element.

For instance, we write

if (!document.getElementById("given-id")) {
  //...
}

to check if getElementById returns null when we try to select an element by its ID.

If it does, then the element with the ID doesn’t exist.

Conclusion

To check if a div does not exist with JavaScript, we can check if null is returned when we try to select an element.

Sometimes, we want to get time zone from user’s browser using moment-timezone and JavaScript.

In this article, we’ll look at how to get time zone from user’s browser using moment-timezone and JavaScript.

How to get time zone from user’s browser using moment-timezone and JavaScript?

To get time zone from user’s browser using moment-timezone and JavaScript, we call the moment.tz.guess method.

For instance, we write

const tz = moment.tz.guess();

to call moment.tz.guess to return the time zone of the device the user’s browser is running on as a string.

Conclusion

To get time zone from user’s browser using moment-timezone and JavaScript, we call the moment.tz.guess method.

Sometimes, we want to apply trim function to each string in an array with JavaScript.

In this article, we’ll look at how to apply trim function to each string in an array with JavaScript.

How to apply trim function to each string in an array with JavaScript?

To apply trim function to each string in an array with JavaScript, we can use the array map method.

For instance, we write

const trimmedArr = arr.map((s) => s.trim());

to call arr.map with a callback that returns the trimmed version of each string we get from calling s.trim.

And then we assign the returned array to trimmedArr.

Conclusion

To apply trim function to each string in an array with JavaScript, we can use the array map method.

Sometimes, we want to create unique ID with JavaScript.

In this article, we’ll look at how to create unique ID with JavaScript.

How to create unique ID with JavaScript?

To create unique ID with JavaScript, we can use the Math.random method.

For instance, we write

const id = Math.random().toString(16).slice(2);

to call the Math.random method to return a random number between 0 and 1.

Then we call toString with 16 on the returned number to convert it to a hex string.

Next, we call slice with 2 to return the string from index 2 to the end of it.

Conclusion

To create unique ID with JavaScript, we can use the Math.random method.