原生js获取复选框的值

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obj = document.getElementsByName("dk_tj");
var longtxt = "";
for (k in obj) {
    if (obj[k].checked) longtxt += obj[k].value + ',';
}
if (longtxt.length > 0) {
    longtxt = longtxt.substring(0, longtxt.length - 1);
}
console.log(longtxt);

​打印成功，并且去掉末尾，号！！！