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This article introduces the relevant knowledge of "how to use the Node.js function". Many people will encounter such a dilemma in the operation of actual cases, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Node.js function

In JavaScript, one function can take an argument as another function. We can define a function first and then pass it, or we can define the function directly where the parameters are passed.

The use of functions in Node.js is similar to Javascript. For example, you can do this:

Function say (word) {

Console.log (word)

}

Function execute (someFunction, value) {

SomeFunction (value)

}

Execute (say, "Hello")

In the above code, we pass the say function as the first variable of the execute function. What is returned here is not the return value of say, but the say itself!

In this way, say becomes the local variable someFunction in execute, and execute can use the say function by calling someFunction () (in parentheses).

Of course, because say has a variable, execute can pass such a variable when calling someFunction.

. . .

Anonymous function http://www.iis7.com/a/lm/zzxzgj/

We can pass a function as a variable. But we don't have to go around the circle of "define and then pass". We can define and pass this function directly in parentheses of another function:

Function execute (someFunction, value) {

SomeFunction (value)

}

Execute (function (word) {console.log (word)}, "Hello")

We define the function we are going to pass to execute directly where execute accepts the first argument.

In this way, we don't even have to name this function, which is why it is called an anonymous function.

. . .

How function passing makes the HTTP server work

With this knowledge in mind, let's take a look at our simple but not simple HTTP server:

Var http = require ("http")

Http.createServer (function (request, response) {

Response.writeHead (200,{ "Content-Type": "text/plain"})

Response.write ("Hello World")

Response.end ()

}) .customers (8888)

Now it should look much clearer: we passed an anonymous function to the createServer function.

The same can be achieved with code like this:

Var http = require ("http")

Function onRequest (request, response) {

Response.writeHead (200,{ "Content-Type": "text/plain"})

Response.write ("Hello World")

Response.end ()

}

Http.createServer (onRequest) .clients (8888)

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