LemonadeJS events

This chapter will describe more about the two native events and the JavaScript event object (e).

Event	Description
onload(component: DOMElement)	It happens when the component is mounted and ready in the DOM. `self.onload(component: DOMElement) => void`
onchange(property, affectedElements)	It happens when the value of a self property in observation is updated. `self.onchange(property: string, affected: object) => void` `@param property` - self property that triggered the event. `@param affectedElements` - When the same property is bound to different HTML elements.

Examples

When a property value changes

There is a call to the method self.onchange when the value of a self property in observation changes. A self property is automatically added to the list of observable properties when this self property is included in the DOM.

<html>
<script src="https://lemonadejs.net/lemonade.js"></script>
<div id='root'></div>
<script>
function Component() {
    // Create the self object
    const self = this;
    self.onchange = function(property) {
        // It will be called when counter is updated
        alert('The self property: ' + property + ' is updated');
    }
    // Create the property
    self.counter = 1;
    // Template
    return `<>
        <div>{{self.counter}}</div>
        <input type="button" value="Counter+1" onclick="self.counter++;"/>
    </>`;
}
// Render the LemonadeJS element into the DOM
lemonade.render(Component, document.getElementById('root'));
</script>
</html>

See this example on codesandbox

When the component is ready

The component method self.onload will be called when the component is ready and appended to the DOM.

<html>
<script src="https://lemonadejs.net/lemonade.js"></script>
<div id='root'></div>
<script>
function Component() {
    // Create the self object
    const self = this;
    self.onload = function(element) {
        // It will be called when the component is ready
        self.container.style.color = 'red';
    }
    // Template
    return `<div :ref="self.container">My component</div>`;
}
// Render the LemonadeJS element into the DOM
lemonade.render(Component, document.getElementById('root'));
</script>
</html>

The event object

From version 2.2.4 you can pass the event object (e) from the template to any event handler, as example below.

<html>
<script src="https://lemonadejs.net/lemonade.js"></script>
<div id='root'></div>
<script>
function Component() {
    // Create the self object
    const self = this;
    self.test = function(e) {
        console.log(e);
        e.preventDefault();
    }
    // The event object will be included
    return `<input type="button" value="Click here" onclick="self.test(e);"/>`;
}
// Render the LemonadeJS element into the DOM
lemonade.render(Component, document.getElementById('root'));
</script>
</html>

The console shows the event object.