I have created a function in global.function.js file as
function getData(flag) {
if (flag === 1) {
return "one";
}
else {
return "not one";
}
}
which then is imported using custom-js-import.html element:
<script src="global.function.js"></script>
When I tried to access the above function in custom-element.html, I am able to access it in the script part but not in the template part.
Is there any way I can access the function inside the HTML element?
<!-- custom-element.html -->
<link rel="import" href="https://polygit.org/components/polymer/polymer-element.html">
<link rel="import" href="custom-js-import.html">
<dom-module id="custom-element">
<template>
<div>
Hello
</div>
<div id="data"></div>
<div>{{getData(1)}}</div><!-- Unable to access this from here -->
<div>{{getLocalData()}}</div>
</template>
<script>
// Define the class for a new element called custom-element
class CustomElement extends Polymer.Element {
static get is() { return "custom-element"; }
constructor() {
super();
}
ready(){
super.ready();
this.$.data.textContent = "I'm a custom-element.";
console.log(getData(1));//can be easily accessed from here
}
getLocalData(){
return "local";
}
}
// Register the new element with the browser
customElements.define(CustomElement.is, CustomElement);
</script>
</dom-module>
Sample Code
Is there any way I can access the function inside the HTML element?
Not really. In order to use data in a template you need to bind it to a property (Polymer calls this data binding).
Polymer's data binding system is designed for binding values to a template. Those values are typically just literals (e.g. strings and numbers) or plain ole javascript objects e.g. {a: 'someval', b: 5}
. Polymer's data binding system is not designed to bind functions to a template and you can't just use javascript inside of a template. (If you're really into that idea, check out React as a replacement to polymer).
The polymer way to do what you're trying to do is to use a computed property. Instead of calling a function inside the template, create a computed property that reacts to changes of other variables. When the state of a property changes, the computed property will change too. This state can be thought of as the argument of your function.
I think it's better just to see the code working yeah (tested in chrome)?
<link rel="import" href="https://polygit.org/components/polymer/polymer-element.html">
<link rel="import" href="custom-js-import.html">
<dom-module id="custom-element">
<template>
<div>
Hello
</div>
<label>
<input type="number" value="{{flag::input}}">
</label>
<h1>from flag: [[flag]]</h1>
<div id="data"></div>
<div>{{boundComputedData}}</div><!-- Unable to access this from here -->
<div>{{getLocalData()}}</div>
</template>
<script>
// Define the class for a new element called custom-element
class CustomElement extends Polymer.Element {
static get is() {
return "custom-element";
}
constructor() {
super();
}
getData(flag) {
const flagAsNumber = parseInt(flag);
if (flagAsNumber === 1) {
return "one";
} else {
return "not one";
}
}
ready() {
super.ready();
this.$.data.textContent = "I'm a custom-element.";
console.log(this.getData(1)); //can be easily accessed from here
}
getLocalData() {
return "local";
}
static get properties() {
return {
flag: {
type: Number,
value: 0
},
boundComputedData: {
type: String,
computed: 'getData(flag)'
}
};
}
}
// Register the new element with the browser
customElements.define(CustomElement.is, CustomElement);
</script>
</dom-module>
<custom-element></custom-element>
So What I'm doing here is:
creating a computed property boundComputedData
and setting the computed
property to 'getData(flag)'
which will make it use the class function getData
.
Now whenever the state the property flag
changes, the computed property will update.
Hope it helps!
Thanks to Rico Kahler for suggesting me to use a mixin. Using mixin solved my problem. You can view the full working sample here.
All the global functions can be defined in the mixin.
<!--custom-mixin.html-->
<script>
const CustomMixin = superclass => class extends superclass {
static get properties() {
return {};
}
connectedCallback() {
super.connectedCallback();
}
getData(flag) {
if (flag === 1) {
return "one(From Mixin)";
} else {
return "not one(From Mixin)";
}
}
};
</script>
And remember to import the mixin file and add that mixin to your element.
<!-- custom-element.html -->
<link rel="import" href="https://polygit.org/components/polymer/polymer-element.html">
<link rel="import" href="custom-mixin.html">
<dom-module id="custom-element">
<template>
<div>
Hello
</div>
<div id="data"></div>
<div>{{getData(1)}}</div>
<!-- Unable to access this from here -->
<div>{{getLocalData()}}</div>
</template>
<script>
// Define the class for a new element called custom-element
class CustomElement extends CustomMixin(Polymer.Element) {
static get is() {
return "custom-element";
}
constructor() {
super();
}
ready() {
super.ready();
this.$.data.textContent = "I'm a custom-element.";
console.log(getData(1)); //can be easily accessed from here
}
getLocalData() {
return "local";
}
}
// Register the new element with the browser
customElements.define(CustomElement.is, CustomElement);
</script>
</dom-module>