uhh apparently i just never committed these

lib/util/template-parameters.js

@@ -27,7 +27,37 @@ export function setEmptyParameter (pageContent, paramName, value) {
  * name.
  */
 const existingParameterRegExp = paramName =>
-	new RegExp(`^( *)\\|( *)${regExpEscape(paramName)}( *)=( *).*$`, 'm');
+	new RegExp(`^( *)\\|( *)${regExpEscape(paramName)}( *)=( *)(.*)$`, 'm');
+
+/**
+ * Gets the value of an existing parameter.
+ * @param {string} pageContent
+ * @param {string} paramName
+ * @returns {string | null} The value, or `null` if the parameter doesn't exist
+ */
+export function readExistingParameter (pageContent, paramName) {
+	let regexp = existingParameterRegExp(paramName);
+	let match;
+	if ((match = pageContent.match(regexp))) {
+		return match[5];
+	}
+	return null;
+}
+
+/**
+ * Sets the value of an existing parameter.
+ * @param {string} pageContent
+ * @param {string} paramName
+ * @param {string} value
+ * @returns {string | null}
+ */
+export function setExistingParameter (pageContent, paramName, value) {
+	const regexp = existingParameterRegExp(paramName);
+	if (pageContent.match(regexp)) {
+		return pageContent.replace(regexp, `$1|$2${paramName}$3=$4${value}`)
+	}
+	return null;
+}
 
 /**
  * Inserts a new parameter before or after an existing parameter.