tdsdk js 问题，一个实例只能订阅一个合约么

<tbody id="futuresInfo">
                            <tr>
                                <th>代码</th>
                                <th>合约名称</th>
                                <th>最新价</th>
                                <th>涨跌</th>
                                <th>涨跌幅</th>
                                <th>成交量</th>
                                <th>持仓量</th>
                                <th style="color: red">基差</th>
                            </tr>
                        </tbody>

$('#futuresInfo').ready(function(){
        var tqsdk = new TQSDK()
        const quote_code = ["KQ.m@DCE.c", "KQ.m@CZCE.ZC", "KQ.m@CZCE.OI"]
        const quote_attr = ['underlying_symbol', 'ins_name', 'last_price', 'change', 'change_percent', 'volume', 'open_interest']
        tqsdk.on('ready', function() {
            var futures_info = document.getElementById('futuresInfo')
            for (var i=0; i<quote_code.length; i++) {
                tqsdk.subscribe_quote(quote_code[i])
                var quote = tqsdk.get_quote(quote_code[i])
                let contract_row = document.createElement("tr")
                for (var k=0; k<quote_attr.length; k++) {
                    let contract_info = document.createElement("td")
                    let attr = document.createAttribute("id")
                    attr.value = quote.underlying_symbol.split(".")[1] + '_' + quote_attr[k]
                    contract_info.setAttributeNode(attr)
                    if (quote_attr[k] == 'underlying_symbol') {
                        contract_info.innerHTML = quote[quote_attr[k]].split(".")[1]
                    }
                    else if (quote_attr[k] == 'ins_name') {
                        contract_info.innerHTML = quote[quote_attr[k]]
                    }
                    contract_row.appendChild(contract_info)
                }
                futures_info.appendChild(contract_row)
            }
            tqsdk.on('rtn_data', function() {
                for (var m=0; m<quote_code.length; m++) {
                    var quote = tqsdk.get_quote(quote_code[m])
                    for (var n=2; n<=quote_attr.length; n++) {
                        let data_cell = document.getElementById(quote.underlying_symbol.split(".")[1] + '_' + quote_attr[n])
                        data_cell.innerHTML = ((m, n) => {if (typeof quote[quote_attr[n]] == 'number') {return quote[quote_attr[n]].toFixed(2)} else {return '-'}})()
                    }
                }
            })
        })
    })

想实现各主力合约的价格监控，只能实现最后订阅的合约的信息反馈，之前订阅的合约没有信息反馈