Category: JavaScript

Sometimes, we want to use jQuery to check whether at least one checkbox is checked.

In this article, we’ll look at how to use jQuery to check whether at least one checkbox is checked.

How to use jQuery to check whether at least one checkbox is checked?

To use jQuery to check whether at least one checkbox is checked, we can selected the checked checkboxes and get the length of that.

For instance, we write:

<form>
  <input type="checkbox" value="true" checked="true" name="chk[120]">
  <input type="checkbox" value="true" checked="true" name="chk[128]">
  <input type="checkbox" name="chk[130]">
  <input type="checkbox" name="chk[143]">
  <input type="submit" name="btnsubmit" value="Submit">
</form>

to add a form with some checkboxes.

Then we write:

const someChecked = $('form input:checked').length > 0
console.log(someChecked)

We select the checked checkboxes with $('form input:checked').

And we use length to get the number of checked checkboxes selected.

Therefore, someChecked should be true since some checkboxes are checked.

Conclusion

To use jQuery to check whether at least one checkbox is checked, we can selected the checked checkboxes and get the length of that.

Sometimes, we want to get the first element rather than using [0] in jQuery.

In this article, we’ll look at how to get the first element rather than using [0] in jQuery.

How to get the first element rather than using [0] in jQuery?

To get the first element rather than using [0] in jQuery, we can use the get method.

For instance, we write:

<div>
  foo
</div>
<div>
  bar
</div>
<div>
  baz
</div>

to add a few divs.

Then we write:

const el = $('div').get(0) 
console.log(el)

to select all the divs with $.

Then we call get with 0 to return the first one selected.

Therefore, el is the div with text ‘foo’.

Conclusion

To get the first element rather than using [0] in jQuery, we can use the get method.

Sometimes, we want to get the min/max values among properties of object.

In this article, we’ll look at how to get the min/max values among properties of object.

How to get the min/max values among properties of object?

To get the min/max values among properties of object, we can use the Object.values method to return array with the property values of an object.

Then we can use the Math.min and Math.max to get the min and max value from the array of values respectively.

For instance, we write:

const obj = {
  a: 4,
  b: 0.5,
  c: 0.35,
  d: 5
};

const arr = Object.values(obj);
const min = Math.min(...arr);
const max = Math.max(...arr);

console.log(min, max);

We call Object.values with obj to return an array of obj property values.

Then we call Math.min and Math.max with arr spread into them as arguments to compute the min and max values of arr respectively.

Therefore min is 0.35 and max is 5.

Conclusion

To get the min/max values among properties of object, we can use the Object.values method to return array with the property values of an object.

Then we can use the Math.min and Math.max to get the min and max value from the array of values respectively.

Sometimes, we want to reset all checkboxes using jQuery.

In this article, we’ll look at how to reset all checkboxes using jQuery.

How to reset all checkboxes using jQuery?

To reset all checkboxes using jQuery, we can remove the checked attribute of all checkboxes with prop.

For instance, we write:

<input type='checkbox'>
<input type='checkbox'>
<input type='checkbox'>
<button>
  reset
</button>

to add some checkboxes and a reset button.

Then we write:

$('button').click(() => {
  $('input[type=checkbox]').prop('checked', false);
})

We select the button with $.

And we call click with a click event handler callback.

In the callback, we select all the checkboxes and call prop with 'checked' and false to uncheck all checkboxes.

Conclusion

To reset all checkboxes using jQuery, we can remove the checked attribute of all checkboxes with prop.

Sometimes, we want to clone a JavaScript ES6 class instance.

In this article, we’ll look at how to clone a JavaScript ES6 class instance.

How to clone a JavaScript ES6 class instance?

To clone a JavaScript ES6 class instance, we can use the Object.assign, Object.create, and Object.getPrototypeOf methods.

For instance, we write:

class Foo {}

const orig = new Foo()
const clone = Object.assign(Object.create(Object.getPrototypeOf(orig)), orig)
console.log(clone)

We create a Foo class with class Foo {}.

Then we create an instance of that with new and assign it to orig.

Next, we call Object.prototypeOf with orig to get the prototype of orig.

And we call Object.create with that to create a new object with the same prototype as orig.

And then we merge that with the orig object itself with Object.assign and assign the returned object to clone.

Therefore, clone is also an instance of Foo and inherits from the same prototype.

Conclusion

To clone a JavaScript ES6 class instance, we can use the Object.assign, Object.create, and Object.getPrototypeOf methods.