How to call node js function from html

In JavaScript, a function as a parameter to another function receives. We can define a function, and then pass to be defined directly in the transfer function of the place.

Node.js use a function similar to Javascript, for example, you can do this:

function say(word) {
  console.log(word);
}

function execute(someFunction, value) {
  someFunction(value);
}

execute(say, "Hello");

The above code, we say the function as the first argument execute functions were passed. This return is not the return value of say, but say itself!

Thus, say becomes execute local variables someFunction, execute by calling someFunction () (in the form of parentheses) to say the use of the function.

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

Anonymous function

We can put a function passed as an argument. But we do not have to about this "first defined, and then pass," the circle, we can define another function in parentheses and pass this function:

function execute(someFunction, value) {
  someFunction(value);
}

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

We accept the first argument in the execute directly defines where we are ready to pass to execute the function.

In this way, we do not even have a name for this function, which is why it is called an anonymous function.

Transfer function is how to get HTTP server work

With this knowledge, we 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();
}).listen(8888);

Now it looks much should be clear: we pass an anonymous function to createServer function.

Such a code can also achieve the same purpose:

var http = require("http");

function onRequest(request, response) {
  response.writeHead(200, {"Content-Type": "text/plain"});
  response.write("Hello World");
  response.end();
}

http.createServer(onRequest).listen(8888);

There are many ways to call a JavaScript function in the HTML document, and it is also not a difficult task. First, we have used one of the easiest ways to call a JavaScript function in HTML document:

In this method, we will create and define a function in the HTML document's head section. To invoke this function in the html document, we have to create a simple button and using the onclick event attribute (which is an event handler) along with it, we can call the function by clicking on the button.

To understand it more clearly let's see the given program:

Program

Explanation of program

In the above-given program, we have created a simple HTML document. Inside the head section of the HTML document, we have defined a function (e.g myfunction();) inside the script tags .

On the other hand, inside the body section, we displayed some text and created a button. To call our function, we have used the onclick attribute along with the button and when the user clicks on that button our function gets executes and display an alert message, as you can see in the output.

Output

Calling a function using external JavaScript file

We can also call JavaScript functions using an external JavaScript file attached to our HTML document. To do this, first we have to create a JavaScript file and define our function in it and save itwith (.Js) extension.

Once the JavaScript file is created, we need to create a simple HTML document. To include our JavaScript file in the HTML document, we have to use the script tag