AST 【抽象语法树 Abstract Syntax Trees】

代码转成语法树： astexplorer.net/

• esprima把源码转化为AST
• estraverse 遍历并更新AST
• escodegen将AST重新生成源码

// npm i esprima estraverse escodegen -S
 1. ast: 
{
  "type": "Program",
  "start": 0,
  "end": 17,
  "body": [
    {
      "type": "FunctionDeclaration",
      "start": 0,
      "end": 17,
      "id": {
        "type": "Identifier",
        "start": 9,
        "end": 12,
        "name": "abc"
      },
      "expression": false,
      "generator": false,
      "async": false,
      "params": [],
      "body": {
        "type": "BlockStatement",
        "start": 15,
        "end": 17,
        "body": []
      }
    }
  ],
  "sourceType": "module"
}
  
  
 2.遍历
  进入Program
    进入FunctionDeclaration
        进入Identifier
        离开Identifier
        进入BlockStatement
        离开BlockStatement
    离开FunctionDeclaration
离开Program