How to measure execution time of javascript code with callbacks
I have a piece of javascript code that I am executing using the node.js interpreter.
for(var i = 1; i < LIMIT; i++){
db.users.save({id : i, name : "MongoUser [" + i + "]"}, function(err, saved) {
if( err || !saved ) console.log("Error");
else console.log("Saved");
});
}
I want to know how to measure the time taken by these db insert operations. I could compute the difference of Date values after and before this piece of code but that would be incorrect because of the asynchronous nature of the code.
使用Node.js console.time()和console.timeEnd() ：
var i;
console.time("dbsave");
for(i = 1; i < LIMIT; i++){
db.users.save({id : i, name : "MongoUser [" + i + "]"}, end);
}
end = function(err, saved) {
console.log(( err || !saved )?"Error":"Saved");
if(--i === 1){console.timeEnd("dbsave");}
};
There is a method that is designed for this. Check out process.hrtime(); .
So, I basically put this at the top of my app.
var start = process.hrtime();
var elapsed_time = function(note){
var precision = 3; // 3 decimal places
var elapsed = process.hrtime(start)[1] / 1000000; // divide by a million to get nano to milli
console.log(process.hrtime(start)[0] + " s, " + elapsed.toFixed(precision) + " ms - " + note); // print message + time
start = process.hrtime(); // reset the timer
}
Then I use it to see how long functions take. Here's a basic example that prints the contents of a text file called "output.txt":
var debug = true;
http.createServer(function(request, response) {
if(debug) console.log("----------------------------------");
if(debug) elapsed_time("recieved request");
var send_html = function(err, contents) {
if(debug) elapsed_time("start send_html()");
response.writeHead(200, {'Content-Type': 'text/html' } );
response.end(contents);
if(debug) elapsed_time("end send_html()");
}
if(debug) elapsed_time("start readFile()");
fs.readFile('output.txt', send_html);
if(debug) elapsed_time("end readFile()");
}).listen(8080);
Here's a quick test you can run in a terminal (BASH shell):
for i in {1..100}; do echo $i; curl http://localhost:8080/; done
Invoking console.time('label') will record the current time in milliseconds, then later calling console.timeEnd('label') will display the duration from that point.
The time in milliseconds will be automatically printed alongside the label, so you don't have to make a separate call to console.log to print a label:
console.time('test');
//some code
console.timeEnd('test'); //Prints something like that-> test: 11374.004ms
For more information, see Mozilla's developer docs on console.time .
上一篇: 停止被缓存的jQuery .load响应