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Two-way data binding with LemonadeJS

The special attributes

The LemonadeJS attributes are special HTML attributes you can append to an HTML tag. There are four native LemonadeJS attributes, they are the @ref, @bind, @loop and @ready. In this section we will go through each of them with examples.

Summary of this chapter

Each of the four special LemonadeJS attributes starts with @ and can be included any HTML tags, such as:

**@ref** add a property in the self that keeps a reference to the DOM element. <div @ref="self.myDiv"></div> **@bind** is used to create a two-way binding between a tag and the specified self property. <input type="text" @bind="self.name" /> **@ready** is a method which will be executed when the element is ready and appended to the DOM. <div @ready="self.ready(this)"></div> **@loop** is a attribute used in custom lemonadeJS components to render a HTML based on an array of objects. <List @loop="self.myArray" />

Alternative Syntax

Alternatively, you can use the following properties lm-ref, lm-bind, lm-loop and lm-ready for the same purpose.

Create a reference with @ref

The @ref creates a property in the self as a reference to the element defined in the template.

<html>
<script src="https://lemonadejs.com/v2/lemonade.js"></script>
<div id='root'></div>
<script>
var Reference = (function() {
    var self = {};
    self.update = function() {
        self.text.style.color = 'red';
    }

    var template = `<>
        <input value='Any text' @ref='self.text' />
        <input type='button' onclick='self.update()'value='Update' />
        </>`;

    return lemonade.element(template, self);
});

lemonade.render(Reference, document.getElementById('root'));
</script>
</html>

See this example on codesandbox

Tracking changes with @bind

The @bind helps to link a self property to the HTML element value. Thus helping to keep the synchronization the desired property and the component value.

<html>
<script src="https://lemonadejs.com/v2/lemonade.js"></script>
<div id='root'></div>
<script>
var Tracking = (function() {
    var self = {};

    // Default value for this property = default value for the dropdown
    self.name = 'Ringo';

    var template = `<>
        <span>{{self.name}}</span><br/><br/>
        <select @bind='self.name'>
        <option>John</option>
        <option>Paul</option>
        <option>George</option>
        <option>Ringo</option>
        </select>
        </>`;

    return lemonade.element(template, self);
});
lemonade.render(Tracking, document.getElementById('root'));
</script>
</html>

See this example on codesandbox

When an element is @ready

The @ready will call the defined method when the element is ready and appended into the DOM.

<html>
<script src="https://lemonadejs.com/v2/lemonade.js"></script>
<div id='root'></div>
<script>
var Ready = (function() {
    var self = {};

    // Execute the method when the element is mount
    self.getWidth = function(element) {
        self.width = element.offsetWidth;
    }

    var template = `<>
        <input @ready='self.getWidth(this)'/>
        <i>The input width is: {{self.width}}</i>
    </>`;

    return lemonade.element(template, self);
});
lemonade.render(Ready, document.getElementById('root'));
</script>
</html>

See this example on codesandbox

Component lists from an array of objects using @loop

The @loop creates a list of elements based on a template from an array of objects.

<html>
<script src="https://lemonadejs.com/v2/lemonade.js"></script>
<div id='root'></div>
<script>
var Mylist = (function() {
    // Create one self for each interaction in the array
    var self = this;
    // Template
    var template = `<li>
            <b>{{self.title}}</b><br>
            <i>{{self.description}}</i>
        </li>`;

    return lemonade.element(template, self);
});

var Loop = (function() {
    var self = {};

    self.rows = [
        {
            title:'Google',
            description: 'The alpha search engine...'
        },
        {
            title:'Bind',
            description: 'The microsoft search engine...'
        },
    ];

    // @loop only can be used in custom elements
    var template = `<ul><Mylist @loop="self.rows" /></ul>`;

    return lemonade.element(template, self, { Mylist });
});
lemonade.render(Loop, document.getElementById('root'));
</script>
</html>

See this example on codesandbox

Next chapter

We will explore each of those LemonadeJS attributes in the next few chapters. In the next one, we will give focus on the @bind and the HTML form element two-way binding.

Next chapter: Two way binding

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