“Многочисленные формы FormData JS” Ответ

Многочисленные формы FormData JS

var a = new FormData(); // using additional FormData object
var b = [];             // using an array
for(var i = 0; i < document.forms.length; i++){
    var form = document.forms[i];
    var data = new FormData(form);
    var formValues = data.entries()
    while (!(ent = formValues.next()).done) {

        // Note the change here 
        a.append(`${ent.value[0]}[]`, ent.value[1])
    }
}
// here a will include all the data from all of your forms.