Category: JavaScript Answers

Sometimes, we want to expect arrays to be equal ignoring order with Jest and JavaScript.

In this article, we’ll look at how to expect arrays to be equal ignoring order with Jest and JavaScript.

How to expect arrays to be equal ignoring order with Jest and JavaScript?

To expect arrays to be equal ignoring order with Jest and JavaScript, we can use the toEqual method to compare an array of primitive values.

For instance, we write

expect(array1.sort()).toEqual(array2.sort());

to call sort to sort array1 and array2.

Then we call toEqual with the sorted version of array2 to see if it’s the same as the sorted version of array1.

This works if array1 and array2 only have primitive values.

If they don’t have primitive values, then we’ve to convert them to arrays that have primitive values.

For instance, we write

const array1 = [{ id: 1 }, { id: 2 }, { id: 3 }];
const array2 = [{ id: 3 }, { id: 2 }, { id: 1 }];

expect(array1.map((a) => a.id).sort()).toEqual(array2.map((a) => a.id).sort());

to call map to map both arrays to arrays with only the id property values.

And then we do the comparisons.

Conclusion

To expect arrays to be equal ignoring order with Jest and JavaScript, we can use the toEqual method to compare an array of primitive values.

Sometimes, we want to use regex to replace everything except numbers and a decimal point with JavaScript.

In this article, we’ll look at how to use regex to replace everything except numbers and a decimal point with JavaScript.

How to use regex to replace everything except numbers and a decimal point with JavaScript?

To use regex to replace everything except numbers and a decimal point with JavaScript, we can use the string replace method.

For instance, we write

const n = number.replace(/(\.\d+)+/, "");

to replace all digits after the decimal point with empty strings.

Conclusion

To use regex to replace everything except numbers and a decimal point with JavaScript, we can use the string replace method.

Sometimes, we want to create JavaScript array (JSON format) dynamically.

In this article, we’ll look at how to create JavaScript array (JSON format) dynamically.

How to create JavaScript array (JSON format) dynamically?

To create JavaScript array (JSON format) dynamically, we call the array push method.

For instance, we write

const students = [];
const obj = {
  firstName: name,
  lastMame: name,
  age: age,
};
students .push(obj);

to call students.push with obj to add the obj object as the last entry of the students array.

Conclusions

To create JavaScript array (JSON format) dynamically, we call the array push method.

Sometimes, we want to start the week on Monday with isoWeekday() with JavaScript.

In this article, we’ll look at how to start the week on Monday with isoWeekday() with JavaScript.

How to start the week on Monday with isoWeekday() with JavaScript?

To start the week on Monday with isoWeekday() with JavaScript, we call startOf with 'week' before calling isoWeekday.

For instance, w write

const begin = moment(date).startOf("week").isoWeekday(1);

to call startOf on the moment object to get the start of the week.

And then we call isoWeekday with 1 to set the start of the week to Monday.

Conclusion

To start the week on Monday with isoWeekday() with JavaScript, we call startOf with 'week' before calling isoWeekday.

Sometimes, we want to detect if a user is already logged in Firebase with JavaScript.

In this article, we’ll look at how to detect if a user is already logged in Firebase with JavaScript.

How to detect if a user is already logged in Firebase with JavaScript?

To detect if a user is already logged in Firebase with JavaScript, we can call the onAuthStateChanged method.

For instance, we write

firebase.auth().onAuthStateChanged((user) => {
  if (user) {
    // ...
  } else {
    // ...
  }
});

to call onAuthStateChanged with a callback that checks if the user is set.

If user is set, then the user is logged in.

Otherwise, the user isn’t logged in.

Conclusion

To detect if a user is already logged in Firebase with JavaScript, we can call the onAuthStateChanged method.