Shim and Polyfill in [concept collection]

• shim

  ---

  Is a small class library （lib）, Provide independent API, To make up for the compatibility problem that people need to consider when using native languages in different environments .

  such as ： Use js Native Ajax In operation , Do you use XMLHttpRequest establish xhr object , But in IE8 On , You have to use ActiveXObject, To solve these compatibility problems , At the same time, simplify the operation ,jQuery There is .

  jQuery The core idea is ： write less,do more！ therefore ,jQuery Can be seen as a shim.

• polyfill

  ---

  Is a small class library （lib）, It's used to implement native that browsers don't support API Code for .

  such as ：IE9 The following is not supported html5 Some new labels , have access to HTML5 shim For compatibility ; Older browsers don't support ES6 as well as ES6+ Some new features of , have access to Babel To compile into ES5 Syntax compatible .

  The code example is as follows ：

  if (!window.XMLHttpRequest) {
        
    window.XMLHttpRequest = function () {
         .... }
  }
  

  Be careful

  Native API Code for , It can be called polyfill Class library of , The solution must be in an incompatible environment , Redefinition JS Its own grammar , Will not redefine API.

• shim and polyfill

  ---

  1,shim and polyfill The purpose of is to solve browser compatibility , And provide convenient , This is also a class library （lib） One of the functions of ;
  2,shim Contains polyfill, Wider scope , You can redefine API, and polyfill Relatively narrow ,API It must be JS standard ;