增加 msg.payload[i] 变量

Question

我有一个包含两列的 MySQL 数据库：用户名 和密码。我想一一列出用户名。

第一个函数保存我的数据库查询：

msg.topic = "SELECT * FROM userlog";
return msg;

第二个函数循环直到显示所有数据库用户名。 maxarray 是我的数据库中用户名的最大数量。

var maxarray = global.get("maxarray");
var i;

for (i = 0; i < maxarray; i++) {
    msg.payload = msg.payload[i].Username;
    node.send(msg);
}

return;

每当我运行这个，它给我一个错误：

"TypeError: Cannot read property '2' of undefined"

如果你想导入，这是我的流程。

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Answer 1

您需要在循环之前获取 msg.payload 的副本，因为您在发送 msg 对象之前已经替换了它。

您可能还应该使用数组长度，而不是试图在全局变量中保持跟踪

var i;
var array = msg.payload

for (i = 0; i < array.length; i++) {
    msg.payload = array[i].Username;
    node.send(msg);
}

return;

增加 msg.payload[i] 变量

Increasing the msg.payload[i] variable

javascript

node.js

node-red