Category: JavaScript Answers

Sometimes, we want to change the content of a text area with JavaScript.

In this article, we’ll look at how to change the content of a text area with JavaScript.

How to change the content of a text area with JavaScript?

To change the content of a text area with JavaScript, we can set the value property of it.

For instance, we write

document.getElementById('myTextarea').value = '';

to select the text area with ID myTextArea with getElementById.

And then we set its value property to an empty string to empty the text area.

The text area is something like

<textarea id="myTextarea">foobar</textarea>

Conclusion

To change the content of a text area with JavaScript, we can set the value property of it.

Sometimes, we want to get element inside element by class and ID with JavaScript.

In this article, we’ll look at how to get element inside element by class and ID with JavaScript.

How to get element inside element by class and ID with JavaScript?

To get element inside element by class and ID with JavaScript, we can get the parent element.

And then we call the method to select the child element in the parent.

For instance, we write

const targetDiv = document
  .getElementById("foo")
  .getElementsByClassName("bar")[0];

to call getElementById to get the parent element with ID foo.

Then we call getElementsByClassName with 'bar' to select the elements with class bar in the element with ID foo.

Conclusion

To get element inside element by class and ID with JavaScript, we can get the parent element.

And then we call the method to select the child element in the parent.

Sometimes, we want to find variable type in JavaScript.

In this article, we’ll look at how to find variable type in JavaScript.

How to find variable type in JavaScript?

To find variable type in JavaScript, we can use the typeof operator.

For instance, we write

typeof "foo"

to return 'string' since 'foo' is a string.

We can use this with other primitive values like numbers and booleans. It also works with functions.

Conclusion

To find variable type in JavaScript, we can use the typeof operator.

Sometimes, we want to extend an object in JavaScript.

In this article, we’ll look at how to extend an object in JavaScript.

How to extend an object in JavaScript?

To extend an object in JavaScript, we can use the Object.create method.

For instance, we write

const person = {
  name: "",
  greet() {
    console.log(`Hi, I am ${this.name}.`);
  },
};

const jack = Object.create(person);
jack.name = "Jack";
jack.greet();

to call Object.create with person to create an object that inherits the prototypes of person and the properties in person.

Then we add the name property to the jack object and call greet on it.

The greet method then should log 'Hi, I am Jack.'.

Conclusion

To extend an object in JavaScript, we can use the Object.create method.

Sometimes, we want to count a JavaScript object’s attributes.

In this article, we’ll look at how to count a JavaScript object’s attributes.

How to count a JavaScript object’s attributes?

To count a JavaScript object’s attributes, we can use the Object.keys method.

For instance, we write

Object.keys(myObject).length;

to call Object.keys with myObject to get an array of non-inherited property keys in myObject.

Then we use the length property to get the number of properties in myObject.

Conclusion

To count a JavaScript object’s attributes, we can use the Object.keys method.