55 lines
1.9 KiB
TypeScript
55 lines
1.9 KiB
TypeScript
// Utilities for processing HTML element attributes
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import { ElementRef } from '@angular/core';
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export interface AttrMap {
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[key: string]: string;
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}
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/**
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* Get attribute map from element or ElementRef `attributes`.
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* Attribute map keys are forced lowercase for case-insensitive lookup.
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* @param el The source of the attributes.
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*/
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export function getAttrs(el: HTMLElement | ElementRef): AttrMap {
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const attrs: NamedNodeMap = el instanceof ElementRef ? el.nativeElement.attributes : el.attributes;
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const attrMap: AttrMap = {};
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for (const attr of attrs as any as Attr[] /* cast due to https://github.com/Microsoft/TypeScript/issues/2695 */) {
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attrMap[attr.name.toLowerCase()] = attr.value;
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}
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return attrMap;
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}
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/**
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* Return the attribute that matches `attr`.
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* @param attr Name of the attribute or a string of candidate attribute names.
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*/
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export function getAttrValue(attrs: AttrMap, attr: string | string[]): string | undefined {
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const key = (typeof attr === 'string')
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? attr
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: attr.find(a => attrs.hasOwnProperty(a.toLowerCase()));
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return (key === undefined) ? undefined : attrs[key.toLowerCase()];
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}
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/**
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* Return the boolean state of an attribute value (if supplied)
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* @param attrValue The string value of some attribute (or undefined if attribute not present).
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* @param def Default boolean value when attribute is undefined.
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*/
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export function boolFromValue(attrValue: string | undefined, def: boolean = false) {
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return attrValue === undefined ? def : attrValue.trim() !== 'false';
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}
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/**
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* Return the boolean state of attribute from an element
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* @param el The source of the attributes.
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* @param atty Name of the attribute or a string of candidate attribute names.
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* @param def Default boolean value when attribute is undefined.
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*/
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export function getBoolFromAttribute(
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el: HTMLElement | ElementRef,
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attr: string | string[],
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def: boolean = false): boolean {
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return boolFromValue(getAttrValue(getAttrs(el), attr), def);
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}
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