caches.delete() not working

[thomkok18]

I am building a service worker. The code works, but for some reason yuicompressor is not minifing the code, because of caches.delete();

My code

self.addEventListener('activate', function (e) {
    // console.log("service worker has been activated");

    e.waitUntil(caches.keys().then(function (cacheNames) {
        return Promise.all(cacheNames.filter(function (key) {
            return key !== staticCache;
        }).map(function (key) {
             return caches.delete(key); // error occurs here
        }));
    }));
});

Yuicompressor error

"D:\Program Files\JetBrains\IntelliJ IDEA 2019.2.4\jbr/bin/java" -jar D:\xampp\htdocs\portfolio-thom\node_modules\yuicompressor\build\yuicompressor-2.4.8.jar sw.js -v -o sw.min.js

[INFO] Using charset UTF-8
[ERROR] in sw.js
  36:34:missing name after . operator
[ERROR] in sw.js
  1:0:Compilation produced 1 syntax errors.
org.mozilla.javascript.EvaluatorException: Compilation produced 1 syntax errors.
    at com.yahoo.platform.yui.compressor.YUICompressor$1.runtimeError(YUICompressor.java:172)
    at org.mozilla.javascript.Parser.parse(Parser.java:396)
    at org.mozilla.javascript.Parser.parse(Parser.java:340)
    at com.yahoo.platform.yui.compressor.JavaScriptCompressor.parse(JavaScriptCompressor.java:315)
    at com.yahoo.platform.yui.compressor.JavaScriptCompressor.<init>(JavaScriptCompressor.java:536)
    at com.yahoo.platform.yui.compressor.YUICompressor.main(YUICompressor.java:147)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at com.yahoo.platform.yui.compressor.Bootstrap.main(Bootstrap.java:21)

Process finished with exit code 2

[vl-80]

Try using a different notation for accessing the delete method:

return caches["delete"](key);