vue.config.js：未解析的变量或类型module =>无法找到php文件

I am trying to fetch some data from a database via a php-file. When I try to load the data I get the following error message in the browsers console: “GET http://localhost:8080/api/call_evm.php 404 (Not Found)”.

This is the corresponding method:

methods: {
    lade_daten: function () {
        let vm = this;
        $.getJSON("/api/call_evm.php", function(result){
            vm.datas = result;
        });
    }
},

mounted(){
    this.lade_daten();
}

My vue.config.js looks like this:

module.exports = {
    devServer: {
        proxy: {
            '/api': {
                target: 'http://localhost/evm-formular/api',
                changeOrigin: true,
                pathRewrite: {
                    '^/api': ''
                }
            }
        } 
    },
    runtimeCompiler: true,
    configureWebpack: {
        devtool: 'source-map'
    },
    chainWebpack: config => {
        config.externals({
            jquery: 'jQuery',
            select2:'select2'
        })
    }
}

When I hover the mouse arrow over the keyword module I get the following tooltip: “Unresolved variable or type module”

What does it mean? What can I do?

Thanks a lot!