Data fixes, fix for <img> with 2+ src attributes

src/data.js

@@ -5,20 +5,15 @@ class Data {
 	#expression;
 
 	constructor(obj, expression) {
+		// xml2js returns leaf nodes as strings, turn those into consistent objects
+		// I found this to be safer and more efficient than using the explicitCharkey option
 		this.#obj = typeof obj === 'string' ? { _: obj } : obj;
+
+		// this identifies how the object was referenced, helps a ton with debugging
 		this.#expression = expression;
 	}
 
-	get value() {
-		const value = this.#obj._;
-		if (value === undefined) {
-			throw new Error(`Could not get value from ${this.#expression}.`);
-		}
-
-		return value;
-	}
-
-	#buildExpression(propName, index) {
+	#buildExpression(propName, index = undefined) {
 		let expression = `${this.#expression}.${propName}`;
 		if (index !== undefined) {
 			expression += `[${index}]`;
@@ -27,11 +22,22 @@ class Data {
 		return expression;
 	}
 
+	// used by "optional" functions to return undefined instead of throwing an error
+	#optional(func) {
+		try {
+			return func();
+		} catch (ex) {
+			return undefined;
+		}
+	}
+
+	// will not throw an error if property doesn't exist, defaults to empty array
 	children(propName) {
 		const nodes = this.#obj[propName] ?? [];
 		return nodes.map((value, index) => new Data(value, this.#buildExpression(propName, index)));
 	}
 
+	// throws an error if property (or index on property) doesn't exist
 	child(propName, index = 0) {
 		const nodes = this.#obj[propName];
 		if (nodes === undefined) {
@@ -46,10 +52,22 @@ class Data {
 		return new Data(node, this.#buildExpression(propName, index));
 	}
 
+	// convenience function, since it's very common to want the value of a child
 	childValue(propName, index = 0) {
-		return this.child(propName, index).value;
+		return this.child(propName, index).value();
+	}
+	
+	// throws an error if this object doesn't have a value string
+	value() {
+		const value = this.#obj._;
+		if (value === undefined) {
+			throw new Error(`Could not get value from ${this.#expression}.`);
+		}
+
+		return value;
 	}
 
+	// throws an error if attribute does not exist
 	attribute(attrName) {
 		const attribute = this.#obj.$?.[attrName];
 		if (attribute === undefined) {
@@ -58,6 +76,18 @@ class Data {
 
 		return attribute;
 	}
+
+	optionalChild(propName, index = 0) {
+		return this.#optional(() => this.child(propName, index));
+	}
+
+	optionalChildValue(propName, index = 0) {
+		return this.#optional(() => this.childValue(propName, index));
+	}
+
+	optionalValue() {
+		return this.#optional(() => this.value());
+	}
 }
 
 export async function load(content) {