For input fields you could use ECMA6 like following:

Get your form in a constant

const form = document.querySelector('form') 

Grab all values:

Object.values(form).reduce((obj,field) => { obj[field.name] = field.value; return obj }, {}) 

Above snippet will produce an object with the input name as key and its value.

For input fields you could use ECMAScript 6 like the following:

Get your form in a constant:

const form = document.querySelector('form') 

Grab all values:

Object.values(form).reduce((obj,field) => { obj[field.name] = field.value; return obj }, {}) 

The above snippet will produce an object with the input name as the key and its value.