var draftMap = new Map();
draftMap.set(0, {'id': 0, 'name': 'draftName', 'value': 90.01});

var list = [
    {'item': [{'id': 0, 'name': 'other name', 'value': NaN}]},
    {'item': [{'id': 1, 'name': 'another name', 'value': 0}]}
];

list = list.map(function(rowDataList) {
    var data = rowDataList.item.map(function(rowData){
        if (draftMap.get(rowData.id)) {
            var draft = draftMap.get(rowData.id);
            rowData.name = (draft.name ? draft.name : rowData.name);
            if(true){
                console.log(rowData.value); //output: NaN
                rowData.value = parseFloat(draft.value ? draft.value : rowData.value);
                console.log(rowData.value); //output: 90.01
                console.log(rowData); //output: {id: 0, name: "draftName", value: NaN}
            }
        }
        return rowData;
    });
    rowDataList.item = data;
    return rowDataList;
});