jQuery events - Beau teaches JavaScript

**Understanding jQuery Events**

When it comes to interacting with web pages using JavaScript, understanding events is crucial. In this article, we will delve into the world of jQuery events and explore what they are, how they work, and how to use them effectively.

**What are jQuery Events?**

In jQuery, events refer to actions that occur when a user interacts with an HTML element on a web page. These interactions can include clicking, hovering, double-clicking, leaving an element, entering an element, and many more. Each of these interactions triggers a specific event in jQuery, which allows developers to respond to those events in various ways.

**Common jQuery Events**

One of the most common events in jQuery is the `click` method. This method binds a function to be executed when an HTML element is clicked. For example, if we select an `

` element and attach the `onclick` event handler like this:

```javascript

$("#paragraph").on("click", function() {

console.log("You click the paragraph");

});

```

When we click on that `

` element, the `console.log` statement is executed. But did you know that we can use shorthand for these events in jQuery? Instead of writing `onclick`, we can write `click`. This makes our code more concise and easier to read.

Another common event in jQuery is the `hover` method. This method binds a function to be executed when an HTML element is hovered over or out of. To demonstrate this, let's say we want to add a paragraph of text and attach both the `Mouse Enter` and `Mouse Leave` events:

```javascript

$("#paragraph").on("click", function() {

console.log("You click the paragraph");

});

```

If we select multiple events using the space character, like this:

```javascript

$("#paragraph").on("click Mouse Enter Mouse Leave", function() {

if (e.type === "mouseover") {

console.log("You hover over the paragraph");

} else if (e.type === "mouseout") {

console.log("You leave the paragraph");

}

});

```

When we enter the `

` element, it will log `"You hover over the paragraph"` to the console. And when we leave the element, it will log `"You leave the paragraph"`.

**Common Form Events**

Form events are essential for handling user interactions with form elements like inputs, selects, and buttons. In jQuery, some common form events include `focus`, `blur`, and `change`. To demonstrate these events, let's say we want to add an input field to our HTML:

```javascript

```

We can then select the input element using jQuery like this:

```javascript

$("#input").on("focus", function() {

console.log("You focus on the input");

});

```

When we click into the input field, it will log `"You focus on the input"` to the console.

Similarly, we can attach a `blur` event handler to the input element like this:

```javascript

$("#input").on("blur", function() {

console.log("You blur the input");

});

```

When we leave the input field, it will log `"You blur the input"` to the console.

**Using the `on` Method**

The `on` method in jQuery is a shorthand for attaching event listeners. It allows us to attach multiple events to an element with a single line of code. For example:

```javascript

$("#paragraph").on("click Mouse Enter Mouse Leave", function(e) {

if (e.type === "mouseover") {

console.log("You hover over the paragraph");

} else if (e.type === "mouseout") {

console.log("You leave the paragraph");

}

});

```

This code attaches both `Mouse Enter` and `Mouse Leave` events to the `

` element. But did you know that we can use an object with key-value pairs in the `on` method? Here's an example:

```javascript

$("#paragraph").on({

click: function() {

console.log("You click the paragraph");

},

mouseover: function() {

console.log("You hover over the paragraph");

}

});

```

This code attaches two event listeners to the `

` element: one for `click` and another for `mouseover`.

**Removing Event Listeners**

Finally, we need to know how to remove event listeners. In jQuery, we can use the `off` method to detach an event listener from an element. For example:

```javascript

$("#paragraph").on("click", function() {

console.log("You click the paragraph");

});

```

If we want to turn off the `click` event handler, we can use the following code:

```javascript

$("#paragraph").off('click');

```

This code removes the `click` event listener from the `

` element.

**The `one` Method**

One of the most interesting methods in jQuery is the `one` method. This method attaches an event listener to an element, but only fires it once when triggered, even if the trigger happens multiple times. For example:

```javascript

$("#paragraph").on("click", function() {

console.log("You click the paragraph");

});

```

If we want to attach a one-time event handler to the `

` element, we can use the following code:

```javascript

$("#paragraph").one('click', function() {

console.log("You click the paragraph for the first time");

});

```

In this example, even if the user clicks on the `

` element multiple times, the `console.log` statement will only be executed once.

That's a wrap! In this article, we explored some of the most essential jQuery events and how to use them effectively. By mastering these events, you'll become proficient in handling interactions with your web pages and creating more responsive user experiences.

"WEBVTTKind: captionsLanguage: enin my last video I introduced jQuery in this video I'm going to talk a little more about jQuery events so here's a basic event so I'm going to select a paragraph tag and then I'm going to attach a click event so when any paragraph is clicked this function right here is run and in the console it's just going to say you clicked a paragraph now in my last video I told you that your code should usually be in a document. ready function to make sure the document is fully loaded before the other code is run while it is still used document. ready is now deprecated and there's a more concise way to do the same thing I'm going to put this whole thing in another function we're going to just put a dollar sign and then we're going to put this in a function here now instead of document. ready it's just dollar sign and then the function so I'm going to take this here and put it right in here there we go let's try this out okay now when I click this paragraph you click the paragraph you click the paragraph you click the paragraph and if I had multiple paragraphs every paragraph would have that same click event so in jQuery most Dom events have an equivalent jQuery method here's some more common ones we have um double click Mouse enter mouse leave Mouse down Mouse up and hover so let me show you some examples of here so if I just put Mouse leave here okay now when I click the paragraph nothing happens but if I make my mouse leave the paragraph it's going to say you click the paragraph it really should say you left the paragraph So double click Mouse enter mouse leave Mouse down Mouse up these are pretty self-explanatory now the hover method takes two functions and is a combination of the mouse enter and mouse leave methods so so the first function is executed when the mouse enters the HTML element and the second function is executed when the mouse leaves the element so let me show you an example of that okay so there's two functions they're just separated with a comma here's the first function comma and then we have the the second function here so if I run that when I enter the paragraph you entered when I leave the paragraph you left I also want to show you some common form events so we have Focus blur and change so if I add an input field here okay so now I'm selecting the input field that I added up above and we're going to do the focus event so in the focus event that just means when it gets focused so if I click into this input field it's going to say you did something down in the console and blur is when you leave the input field and if you do change that's just if the text in the input field changes so if I put hello here it says you did something if I say buy and then it says you did something again because the text changed from Hello to buy I had to hit tab to exit the field before it recognized that the text changed now all of the events I have showed you so far are actually just shorthand for the on method let me show you what I mean so if we go back to the original um click method on the paragraph here so we we have this click event this this could be written differently instead of Click we're going to put on here now we're going to pass in the word click and then we s the function so now it's paragraph onclick So when you click the paragraph you're we're going to run this function and that's going to act just the same way so if I click this paragraph you click the paragraph when you use the on method you can do some additional things for instance it is easy to add multiple events so after click here I'm going to put Mouse enter now you can put any number of events here as long as they are separated by the space character so I'm going to run that now when I enter the paragraph it's going to say you click the paragraph and when I click a paragraph it's going to say you click the paragraph so this will bind the same action to multiple events you can also use the on method to bind different actions you can pass an object into on with one or more key value pairs with the key being the event name and the value being the function to handle the event so here's the example of this inside the on method we have this object here and inside the object there are two key value pairs so key is click the value is the function we're going to run key is mouse over the value is the function we're going to run here so let's run that and see what happens when the mouse goes over it says hovered when I click it says say clicked and you can also remove an event listener with the off method so let me put in this we're going to select a pag. off click we're going to turn the click method off the click event handler off so if I go over the paragraph it's going to say hovered if I click the paragraph nothing's happening I'm clicking but nothing's appearing in the console because we turned off the click Handler and there's one final thing I want to show you which is that you can set up an event to run only once with with the one method you can change the on to one you on now it's one it's just going to run once so before it would show hovered even every time I went over it so I'm going go over it once go off it go over it again and it's not showing hovered again even though I'm moving my mouse on and off of it it only runs one time if you use the one method okay that's jQuery events thanks for watching my name is boars don't forget to subscribe and remember use your code for goodin my last video I introduced jQuery in this video I'm going to talk a little more about jQuery events so here's a basic event so I'm going to select a paragraph tag and then I'm going to attach a click event so when any paragraph is clicked this function right here is run and in the console it's just going to say you clicked a paragraph now in my last video I told you that your code should usually be in a document. ready function to make sure the document is fully loaded before the other code is run while it is still used document. ready is now deprecated and there's a more concise way to do the same thing I'm going to put this whole thing in another function we're going to just put a dollar sign and then we're going to put this in a function here now instead of document. ready it's just dollar sign and then the function so I'm going to take this here and put it right in here there we go let's try this out okay now when I click this paragraph you click the paragraph you click the paragraph you click the paragraph and if I had multiple paragraphs every paragraph would have that same click event so in jQuery most Dom events have an equivalent jQuery method here's some more common ones we have um double click Mouse enter mouse leave Mouse down Mouse up and hover so let me show you some examples of here so if I just put Mouse leave here okay now when I click the paragraph nothing happens but if I make my mouse leave the paragraph it's going to say you click the paragraph it really should say you left the paragraph So double click Mouse enter mouse leave Mouse down Mouse up these are pretty self-explanatory now the hover method takes two functions and is a combination of the mouse enter and mouse leave methods so so the first function is executed when the mouse enters the HTML element and the second function is executed when the mouse leaves the element so let me show you an example of that okay so there's two functions they're just separated with a comma here's the first function comma and then we have the the second function here so if I run that when I enter the paragraph you entered when I leave the paragraph you left I also want to show you some common form events so we have Focus blur and change so if I add an input field here okay so now I'm selecting the input field that I added up above and we're going to do the focus event so in the focus event that just means when it gets focused so if I click into this input field it's going to say you did something down in the console and blur is when you leave the input field and if you do change that's just if the text in the input field changes so if I put hello here it says you did something if I say buy and then it says you did something again because the text changed from Hello to buy I had to hit tab to exit the field before it recognized that the text changed now all of the events I have showed you so far are actually just shorthand for the on method let me show you what I mean so if we go back to the original um click method on the paragraph here so we we have this click event this this could be written differently instead of Click we're going to put on here now we're going to pass in the word click and then we s the function so now it's paragraph onclick So when you click the paragraph you're we're going to run this function and that's going to act just the same way so if I click this paragraph you click the paragraph when you use the on method you can do some additional things for instance it is easy to add multiple events so after click here I'm going to put Mouse enter now you can put any number of events here as long as they are separated by the space character so I'm going to run that now when I enter the paragraph it's going to say you click the paragraph and when I click a paragraph it's going to say you click the paragraph so this will bind the same action to multiple events you can also use the on method to bind different actions you can pass an object into on with one or more key value pairs with the key being the event name and the value being the function to handle the event so here's the example of this inside the on method we have this object here and inside the object there are two key value pairs so key is click the value is the function we're going to run key is mouse over the value is the function we're going to run here so let's run that and see what happens when the mouse goes over it says hovered when I click it says say clicked and you can also remove an event listener with the off method so let me put in this we're going to select a pag. off click we're going to turn the click method off the click event handler off so if I go over the paragraph it's going to say hovered if I click the paragraph nothing's happening I'm clicking but nothing's appearing in the console because we turned off the click Handler and there's one final thing I want to show you which is that you can set up an event to run only once with with the one method you can change the on to one you on now it's one it's just going to run once so before it would show hovered even every time I went over it so I'm going go over it once go off it go over it again and it's not showing hovered again even though I'm moving my mouse on and off of it it only runs one time if you use the one method okay that's jQuery events thanks for watching my name is boars don't forget to subscribe and remember use your code for good\n"