Why you need to avoid using global variables in web development

This time I will bring you why you need to avoid using global variables in web development, and what are the precautions to avoid using global variables in web development. The following is a practical case, let's take a look.

The main problems caused by global variables are: as the amount of code increases, too many global variables will make the code difficult to maintain and prone to bugs. There is no big problem with one or two global variables. It is almost impossible to achieve zero global variables (unless your JS code is not related to any other JS code and just does some things of its own. This situation is very rare, which does not mean that there is no global variable. ).

If you are writing ES6 code, you will find that it is difficult to create a global variable. Unless you explicitly write window.globalVar = 'something', the ES6 module mechanism automatically sets the scope for you. Splitting makes the code you write more maintainable and secure (old JSers have to lament that modern front-end developers are so happy).

If it is code before ES6, you have to pay attention. For example, variables you declare without using var in a function will be directly mounted into global variables (this should be basic knowledge of JS), so modularization is generally implemented through IIFE, and only one global variable is exposed to the outside world (of course, you You can also use third-party module management tools such as RequireJS or YUI module loader to achieve modularization).

window.global = (function () {  var exportVar = {}; // ES5没有let和const，故用var
  // add method and variable to exportVar
  return exportVar;
})();

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the php Chinese website!

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