How to understand the function concept in javascript

What is a function?

A function is an event-driven or reusable block of code that executes when it is called.

Let’s give a small example:

When we click the button, a warning box as shown below will pop up:

Grammar format:

function functionname()
{
    // 执行代码
}

function is the keyword used to define a function.

Note: JavaScript is case-sensitive. The keyword function must be lowercase, and the function must be called with the same case as the function name.

Function with parameters

Syntax format:

function myFunction(var1,var2)
{
代码
}

Example:

After clicking, it will display:

Parameters with return values

The return value is obtained through the return statement accomplish.

Syntax format:

function myFunction()
{
    var x=5;
  return x;
}

Note: Using the return statement does not mean that the entire JavaScript stops execution, just the function. JavaScript will continue executing code from where the function was called.

Example:

Recommended tutorial:js introductory tutorial

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