export function sendPostDataput (postname,arraytosend,cb) {
    let promise=sendPostDatapput(postname,arraytosend);
    promise.then((result) => {cb(result,0);
    }, (err) => {cb(null,err);});
}
function sendPostDatapput (postname,arraytosend) {
    return new Promise((resolve,reject)=> {
        let data= JSON.stringify(arraytosend);
        console.log(data);
        let result= fetch(postname,{
            method: "put",//У Вас "post"
            headers: { 'Accept': 'application/json',
                'Content-Type': 'application/json'},
            body:data
        });
        result.then(function(response) {
            // console.log('response', response)
            let header=response.headers.get('Content-Type');
            console.log('header', header);
            if(header===null){throw "Проблема с откликом";}

           
            return response.text();
        }).then(function(text) {
           
            let result=JSON.parse(text);
            console.log(result);
            if(result.status==="ERROR") {throw result.errormessage;}
            resolve(result);
            // console.log(arr);
          
        }).catch(function(ex) {
            console.log('failed', ex);
            reject(ex);
        });
    });
}

и в коде sendPostDataput("/mypostendpoint",{value:1,value2:34543,value3:"hjjhghg"},(result)=>{console.log(result)});