Category: JavaScript Answers

One way to set the value of an input field with JavaScript is to set the value property of the input element.

For instance, we can write the following HTML:

<input id='mytext'>

Then we can set the value property of the input by writing:

document.getElementById("mytext").value = "My value";

Call the setAttribute Method

Also, we can call the setAttribute method to set the value attribute of the input element.

For instance, we can write:

document.getElementById("mytext").setAttribute('value', 'My value');

We call setAttribute with the attribute name and value to set the value attribute to 'My value' .

Setting the value Property of an Input in a Form

We can also get the input element by using the document.forms object with the name attribute value of the form and the name attribute value of the input element.

For example, we can write the following HTML:

<form name='myForm'>
  <input type='text' name='name' value=''>
</form>

Then we can use it by writing:

document.forms.myForm.name.value = "New value";

The form name value comes first.

Then the name value of the input element comes after it.

document.querySelector

We can use the document.querySelector method to select the input.

For instance, we can write the following HTML:

<input type='text' name='name' value=''>

Then we can write:

document.querySelector('input[name="name"]').value = "New value";

to get the element with querySelector .

We select the input with the name attribute by putting the name key with its value in the square brackets.

Sometimes, we want to get the last item in a JavaScript object.

In this article, we’ll look at how to get the last item in a JavaScript object.

Get the Last Item in a JavaScript Object

To get the last item in a JavaScript object, we can use the Object.entries method to get the key-value pair arrays of an object in an array.

Therefore, we can use it to get the last item of the JavaScript object.

For instance, we can write:

const obj = {
  'a': 'apple',
  'b': 'banana',
  'c': 'carrot'
}
const entries = Object.entries(obj)
const [last] = entries.slice(-1)
console.log(last)

We have the obj object that we want to get the last property from.

Next, we call Object.entries with obj to get an array of key-value pair arrays of obj .

Then we call slice with -1 to return an array with the last entry of entries .

And we destructure that and assign it to last .

Therefore, last is:

["c", "carrot"]

Conclusion

To get the last item in a JavaScript object, we can use the Object.entries method to get the key-value pair arrays of an object in an array.

Therefore, we can use it to get the last item of the JavaScript object.

Sometimes, we want to filter or map nodelists with JavaScript.

In this article, we’ll look at how to filter or map nodelists with JavaScript.

Filter or Map Nodelists with JavaScript

To filter or map nodelists with JavaScript, we can use the spread operator to convert the nodelist to an array.

For instance, if we have the following HTML:

<p>
  foo
</p>
<p>
  bar
</p>

Then we can convert the nodelist with the selected p elements and call map and filter on it by writing:

const nodes = document.querySelectorAll('p')
const texts = [...nodes].map(n => n.textContent)
console.log(texts)
const filtered = [...nodes].filter(n => n.textContent.includes('foo'))
console.log(filtered)

We call document.querySelectorAll to return a nodelist with the p elements.

Then we use the spread operator to spread the items in the nodes nodelist into an array.

And then we call map to map the node array to an array of text.

Then we call filter on the array of nodes with a callback to return the nodes with textContent that includes 'foo' .

Therefore, texts is [“n foon”, “n barn”]

And filtered has an array with the first p element.

Conclusion

To filter or map nodelists with JavaScript, we can use the spread operator to convert the nodelist to an array.

Sometimes, we want to search for the immediate children of an element returned by querySelector.

In this article, we’ll look at how to search for the immediate children of an element returned by querySelector.

Search for the Immediate Children of an Element Returned by querySelector

To search for the immediate children of an element returned by document.querySelector , we can use the :scope pseudoselector.

For instance, if we have the following HTML:

<div>  
  <p>  
    hello world  
  </p>  
</div>

Then we can get the p element given the div by writing:

const getChild = (elem) => {  
  return elem.querySelectorAll(':scope > p');  
};  
const div = document.querySelector('div')  
console.log(getChild(div))

We define the getChild function that calls elem.querySelectorAll to get all the p elements that are the immediate child of the given elem .

Then we get the div with querySelector and assign it to div .

And then we call getChild with div to get the p element in the div in a Nodelist.

Conclusion

To search for the immediate children of an element returned by document.querySelector , we can use the :scope pseudoselector.

Sometimes, we want to position a div in a specific coordinate with JavaScript.

In this article, we’ll look at how to position a div in a specific coordinate with JavaScript.

Position a Div in a Specific Coordinate with JavaScript

We can set the style.top and style.left properties to position a div in a specific coordinate with JavaScript.

For instance, we can write:

<div>  
  hello world  
</div>

Then we can set the position of the div by writing:

const d = document.querySelector('div');  
d.style.position = "absolute";  
d.style.left = '10px';  
d.style.top = '20px';

We get the div with document.querySelector .

Then we set its position CSS property to 'absolute' with:

d.style.position = "absolute";

Then we set the left and top CSS properties with:

d.style.left = '10px';  
d.style.top = '20px';

The unit must be specified for left and top.

Conclusion

We can set the style.top and style.left properties to position a div in a specific coordinate with JavaScript.