setInterval给我TypeError:无法调用未定义的方法'apply'
在下面的脚本中,我计划让我的脚本轮询设备(家庭自动化)以获取状态。我想每5秒做一次。当我运行没有循环(setInterval)的脚本运行正常。循环它第一次运行正常。我第二次收到错误。我用node.js运行脚本
首先是脚本:
//import node module request
var request = require('request');
//function to get status of a device
function wrapper (url, device, filter, service) {
request(url, function (error, response, body) {
if (!error && response.statusCode == 200) {
obj = JSON.parse(body);
for (var i = 0; i < obj[device].states.length; i++) {
if (obj[device].states[i].service === service && obj[device].states[i].variable === filter) {
deviceStatus = obj[device].states[i].value;
console.log("deviceStatus inside function: " + deviceStatus);
//call the compareTime function
compareTime(deviceStatus);
}
}
}
return 3;
});
};
function compareTime() {
var hour = new Date().getHours();
console.log(hour);
if ( 8 <= hour && hour <= 21 ) {
//var deviceStatus = 0;
console.log("deviceStatus :" + deviceStatus);
if (deviceStatus === '1') {
request('url', function (error, response, body) {
if (!error && response.statusCode == 200) {
}
})
request('url', function (error, response, body) {
if (!error && response.statusCode == 200) {
}
})
} else {
console.log("deviceStatus :" + deviceStatus);
}
} else {
console.log("deviceStatus :" + deviceStatus);
}
};
loop = wrapper('url', 'Device_Num_21', 'Status', 'urn:upnp-org:serviceId:SwitchPower1');
//call the function wrapper with arguments
setInterval(loop, 5000);
错误:
node stack.js
deviceStatus inside function: 1
21
deviceStatus :1
timers.js:261
callback.apply(this, args);
^
TypeError: Cannot call method 'apply' of undefined
at wrapper [as _onTimeout] (timers.js:261:14)
at Timer.listOnTimeout [as ontimeout] (timers.js:112:15)
有人可以帮我这个吗?
回答如下:setInterval()
预计它的第一个论点是function
,loop
可以定义为:
function loop() {
wrapper('url', 'Device_Num_21', 'Status', 'urn:upnp-org:serviceId:SwitchPower1');
}
setInterval(loop, 5000);
错误是因为loop
目前持有undefined
value,它不能被视为具有setInterval()
期望的属性的函数或对象。
该值正从wrapper()
返回,目前正在立即调用。