[рони]

dimquea,

<pre>
    <script>
const obj = {
    101: {id: 101, section: 1, value: 876},
    102: {id: 102, section: 2, value: 394},
    103: {id: 103, section: 1, value: 754}
},
sorted = Object.values(obj).reduce((o, v) => {
const {id, section} = v;
if(!o[section]) o[section] = {}
o[section][id] = v;
return o
}, {});
document.write(JSON.stringify(sorted, "", 1))
    </script>
    </pre>