## Evaluating Javascript In Event Handlers

Event handlers are useful by attaching **commands** to elements to execute javascript on the client side.

See [#interactivity-events](#interactivity-events) for more information on event handlers.

<br>

**Note:** Each command you attach to the event handler will be passed 'self' and 'event' (if applicable) as arguments.
'self' is the current element, and 'event' is the event object.

If you use the OnEvent directly, event names may be any [HTML DOM](https://www.w3schools.com/jsref/dom_obj_event.asp) events, or any [HTMX events](https://htmx.org/events/).

Commands:

```go
js.AddAttribute(string, value)
js.RemoveAttribute(string)
js.AddClass(string, value)
js.SetText(string)
js.Increment(count)
js.SetInnerHtml(Ren)
js.SetOuterHtml(Ren)
js.SetDisabled(bool)
js.RemoveClass(string)
js.Alert(string)
js.EvalJs(string) // eval arbitrary js, use 'self' to get the current element as a reference
js.InjectScript(string)
js.InjectScriptIfNotExist(string)
js.GetPartial(PartialFunc)
js.GetPartialWithQs(PartialFunc, Qs)
js.PostPartial(PartialFunc)
js.PostPartialWithQs(PartialFunc, Qs)
js.GetWithQs(string, Qs)
js.PostWithQs(string, Qs)
js.ToggleClass(string)
js.ToggleClassOnElement(string, string)

// The following methods are used to evaluate JS on nearby elements. 
// Use 'element' to get the element as a reference for the EvalJs methods.
js.EvalJsOnParent(string) 
js.EvalJsOnSibling(string, string)
js.EvalJsOnChildren(string, string)
js.SetClassOnParent(string)
js.RemoveClassOnParent(string)
js.SetClassOnChildren(string, string)
js.RemoveClassOnChildren(string, string)
js.SetClassOnSibling(string, string)
js.RemoveClassOnSibling(string, string)

```
For more usages: see https://github.com/maddalax/htmgo/blob/master/htmgo-site/pages/form.go


**Example:** Evaluating arbitrary JS

```go
func MyButton() *h.Element {
	return h.Button(
		h.Text("Submit"),
		h.OnClick(
        // make sure you use 'self' instead of 'this' 
        // for referencing the current element
			h.EvalJs(`
				   if(Math.random() > 0.5) {
				       self.innerHTML = "Success!";
				   }
		       `,
			),
		),
	)
}
```

tip: If you are using Jetbrains IDE's, you can write `// language=js` as a comment above the function call (h.EvalJS) and it will automatically give you syntax highlighting on the raw JS.

```go
// language=js
h.EvalJs(`
     if(Math.random() > 0.5) {
         self.innerHTML = "Success!";
     }
     `,
),
```