javascript methods push (error name expected) [duplicate]

How do I send a value from a variable here?
opinions.${idGoogleUser}.push(articleData);

I need
opinions.id117074500003811940767.push(articleData);

function ioread(){
    let opinions = [];
    let articleData = {
        name: "fghdfghfghjfghfghfghfgh",
        comment: "cool site",
        url: "https://assets.teenvogue.com/photos/5d3875dcc6732300082916c8/16:9/w_2560%2Cc_limit/00-story.jpg",
        email: "[email protected]",
        okres: "Okresy Bratislavy",
        byvanie: "V byte, V dome"
    }
    function reqListenerComments() {
        let idGoogleUser = id117074500003811940767;
        if (this.status === 200) {
            let responseJSON = JSON.parse(this.responseText)
            opinions = JSON.parse(this.responseText)
            //
            console.log(opinions);
            opinions.`${idGoogleUser}`.push(articleData); // ERROR
            console.log(opinions);
            //console.log(this.responseText);

            let postReqSettings = //an object wih settings of the request
                {
                    method: 'POST',
                    headers: {
                        'Content-Type': 'application/json;charset=utf-8',
                    },
                    body: JSON.stringify(opinions)
                }
            fetch(`https://api.npoint.io/7277534d6c85d7e10b53`, postReqSettings)
                .then(response => {      //fetch promise fullfilled (operation completed successfully)
                    if (response.ok) {    //successful execution includes an error response from the server. So we have to check the return status of the response here.
                        return response.json(); //we return a new promise with the response data in JSON to be processed
                    } else { //if we get server error
                        return Promise.reject(new Error(`Server answered with ${response.status}: ${response.statusText}.`)); //we return a rejected promise to be catched later
                    }
                })
                .finally(() =>
                    alert("ok")
                )
        }
    }

    var ajax = new XMLHttpRequest();
    ajax.addEventListener("load", reqListenerComments);
    ajax.open("GET", `https://api.npoint.io/7277534d6c85d7e10b53`, false);
    ajax.send();
}

opinions.${idGoogleUser}.push(articleData);

I need
opinions.id117074500003811940767.push(articleData);