Apply prefer-const lint rule

lib/soap.js

@@ -102,8 +102,8 @@ function event(xml) {
 
 function parameterInfoList(xml) {
   return xml.find("ParameterInfoStruct").map(e => {
-    let param = e.get("Name").text();
-    let value = e.get("Writable").text();
+    const param = e.get("Name").text();
+    const value = e.get("Writable").text();
     let parsed = parseBool(value);
 
     if (parsed === null) {
@@ -122,8 +122,8 @@ function parameterValueList(xml) {
   return xml.find("ParameterValueStruct").map(e => {
     const valueElement = e.get("Value");
     const valueType = valueElement.attr("type").value();
-    let param = e.get("Name").text();
-    let value = valueElement.text();
+    const param = e.get("Name").text();
+    const value = valueElement.text();
     let parsed = value;
     if (valueType === "xsd:boolean") {
       parsed = parseBool(value);
@@ -447,7 +447,7 @@ function request(data, cwmpVersion, warn) {
     }
   }
 
-  let idElement = xml.get(
+  const idElement = xml.get(
     "/soap-env:Envelope/soap-env:Header/cwmp:ID",
     NAMESPACES[rpc.cwmpVersion]
   );