Created
February 24, 2016 12:05
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Au-Class custom attribute for simplifying bound CSS declarations
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import {customAttribute} from 'aurelia-framework'; | |
/** | |
* The au-class custom attribute is intended to simplify aurelia binding code in the standard html class attribute. | |
* | |
* This is an unofficial community proposal to add to Aurelia (aurelia.io) | |
* | |
* Before: | |
<div class="base-class ${foo} ${someVMProp < 10 ? 'red' : ''} ${!otherVMProp ? 'blue' : ''}"></div> | |
* After: | |
<div au-class.bind="['base-class', foo, {red: someVMProp < 10, blue: !otherVMProp}]"></div> | |
*/ | |
@customAttribute('au-class') | |
export class AuClass { | |
classes = new Set(); | |
static inject = [Element]; | |
constructor(element: Element) { | |
this.element = element; | |
} | |
valueChanged(newVal = {}) { | |
let newClasses = new Set(AuClass._extractClasses(newVal)); | |
let removedClasses = [...this.classes].filter(x => !newClasses.has(x)); | |
let addedClasses = [...newClasses].filter(x => !this.classes.has(x)); | |
this.removeClasses(removedClasses); | |
this.addClasses(addedClasses); | |
this.classes = newClasses; | |
} | |
addClasses(classes) { | |
classes.forEach(c => this.element.classList.add(c)) | |
} | |
removeClasses(classes) { | |
classes.forEach(c => this.element.classList.remove(c)) | |
} | |
static _extractClasses(args) { | |
let classesFound; | |
if (args && typeof args === 'string') { | |
classesFound = [args]; | |
} | |
if (Array.isArray(args)) { | |
classesFound = args.reduce((acc, arg) => acc.concat(AuClass._extractClasses(arg)), []); | |
} | |
else if (typeof args === 'object') { | |
classesFound = Object.keys(args).filter(p => args[p]); | |
} | |
return classesFound; | |
} | |
} |
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