JavaScript Callbacks and Splunk
JavaScript Callbacks and Splunk
我正在使用Splunk Javascript API来访问它的一些功能,但我很难理解回调背后的Javascript概念。
文档中的一个示例:
var http = new splunkjs.ProxyHttp("/proxy");
var service = new splunkjs.Service(http, {
username: username,
password: password,
scheme: scheme,
host: host,
port: port,
version: version
});
Async.chain([
// First, we log in
function(done) {
service.login(done);
},
// Perform the search
function(success, done) {
if (!success) {
done("Error logging in");
}
service.search("search index=_internal | head 3", {}, done);
},
// Wait until the job is done
function(job, done) {
Async.whilst(
// Loop until it is done
function() { return !job.properties().isDone; },
// Refresh the job on every iteration, but sleep for 1 second
function(iterationDone) {
Async.sleep(1000, function() {
// Refresh the job and note how many events we've looked at so far
job.fetch(function(err) {
console.log("-- fetching, " + (job.properties().eventCount || 0) + " events so far");
iterationDone();
});
});
},
// When we're done, just pass the job forward
function(err) {
console.log("-- job done --");
done(err, job);
}
);
},
// Print out the statistics and get the results
function(job, done) {
// Print out the statics
console.log("Job Statistics: ");
console.log(" Event Count: " + job.properties().eventCount);
console.log(" Disk Usage: " + job.properties().diskUsage + " bytes");
console.log(" Priority: " + job.properties().priority);
// Ask the server for the results
job.results({}, done);
},
// Print the raw results out
function(results, job, done) {
// Find the index of the fields we want
var rawIndex = utils.indexOf(results.fields, "_raw");
var sourcetypeIndex = utils.indexOf(results.fields, "sourcetype");
var userIndex = utils.indexOf(results.fields, "user");
// Print out each result and the key-value pairs we want
console.log("Results: ");
for(var i = 0; i < results.rows.length; i++) {
console.log(" Result " + i + ": ");
console.log(" sourcetype: " + results.rows[i][sourcetypeIndex]);
console.log(" user: " + results.rows[i][userIndex]);
console.log(" _raw: " + results.rows[i][rawIndex]);
}
// Once we're done, cancel the job.
job.cancel(done);
}
],
function(err) {
callback(err);
}
);
Async.chain在这里被定义为root.chain = function(tasks, callback)
。我的理解是,任务数组中有5个函数,它们一个接一个地执行,并将结果从一个传递到另一个。
然而,我不明白"完成"、"成功"、"工作"answers"结果"是如何定义的,在哪里定义的,或者它们是如何在其职能范围内用作论据的?
function(success, done) {
if (!success) {
done("Error logging in");
}
service.search("search index=_internal | head 3", {}, done);
}
在这里,它是如何测试成功的,并向done()传递字符串的?
以及这两个功能是如何实现的
function(job, done) {// Print out the statics ..}
&
function(results, job, done) { .. }
将结果数据从第一个函数传递到第二个函数?
为这个长问题道歉。
在Javascript中,函数创建新的作用域。这意味着在传递给函数之前,传递的参数的名称并不重要。
var awesomeName = 'bob';
hi(awesomeName);
// name === undefined
function hi(name) {
// name === 'bob';
console.log('hi', name); // Outputs: 'hi bob' in console
}
// name === undefined
正如您所说,每个任务都会调用下一个任务作为回调。最后一个参数始终是下一个任务函数/回调。这意味着Async.chain
可能会在调用每个任务函数之前自动将回调添加到参数的末尾。done
只是分配给回调的一个常规名称。类似地,其他参数只是上一个任务传递的参数的描述性名称。为了了解它们以这种方式命名的原因,您应该查看调用回调的函数。
例如:
service.login(done)
中可能有某种代码可以执行类似的操作:
login: function(callback) {
var successful;
// Do Login logic here and assign true/false to successful
callback(successful);
}
回调是链中的下一个任务,有两个参数success
和done
。success
只是login
传递给它的第一个参数。Async.chain
总是传递另一个参数作为最后一个参数:下一个任务函数,它只是按惯例分配了名称done
。您可以在每个函数中随意命名它,只要您在函数中使用相同的名称即可。
function cb(success, fuzzyCallback) {
if (!success) {
fuzzyCallback('Error!');
}
fuzzyCallback(null);
}
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