AST学习二----babel库使用

2024-03-23 23:04

文章标签 学习使用 babel ast

本文主要是介绍AST学习二----babel库使用，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1.@babel/traverse

@babel/traverse 是一个用于对抽象语法树(AST)进行递归遍历和更新的工具库，它可以通过访问和修改 AST 节点来实现代码转换。

下面是一个简单的示例代码，其中包含了使用 @babel/parser 将 JavaScript 代码解析为 AST，并使用 @babel/traverse 对 AST 进行遍历和更新的过程。

const parser = require("@babel/parser");
const generator = require("@babel/generator").default
const traverse = require("@babel/traverse").default;// 将 JavaScript 代码解析为 AST
const ast = parser.parse(`const double = x => x * 2;const result = double(3);
`);// 遍历 AST，并对所有函数调用进行修改
traverse(ast, {CallExpression(path){if (path.node.callee.name === "double") {path.node.callee.name = "triple";console.log(path.node.arguments[0])path.node.arguments[0] = {type: 'NumericLiteral',value: path.node.arguments[0].value  * 2,};};},
});
// 将修改之后的AST转换为 JavaScript代码
const code = generator(ast).code;
console.log(code);

2.将var 关键字替换成 let关键字。

const {parse} = require('@babel/parser')
const traverse = require('@babel/traverse').default
const generator = require("@babel/generator").defaultconst code = `var a = 111;var b = 222;var c = a + b;
`;
// 将JavaScript代码转化成 AST
const ast = parse(code)// 遍历AST,将所有的 var 声明替换成 let声明
traverse(ast,{VariableDeclaration(path) {if (path.node.kind === 'var') {path.node.kind = 'let'}},
})// 将修改之后的 AST 转换回 JavaScrtpt 代码
const output = generator(ast, {} ,code);
console.log(output.code);

3.将AST转成JavaScript代码

通过@babel/generator可以将修改之后的AST代码转成js代码,示例如下

const gennerator = require('@babel/generator').defaultconst ast = {"type": "File","start": 0,"end": 16,"loc": {"start": {"line": 1,"column": 0,"index": 0},"end": {"line": 1,"column": 16,"index": 16}},"errors": [],"program": {"type": "Program","start": 0,"end": 16,"loc": {"start": {"line": 1,"column": 0,"index": 0},"end": {"line": 1,"column": 16,"index": 16}},"sourceType": "script","interpreter": null,"body": [{"type": "VariableDeclaration","start": 0,"end": 16,"loc": {"start": {"line": 1,"column": 0,"index": 0},"end": {"line": 1,"column": 16,"index": 16}},"declarations": [{"type": "VariableDeclarator","start": 6,"end": 15,"loc": {"start": {"line": 1,"column": 6,"index": 6},"end": {"line": 1,"column": 15,"index": 15}},"id": {"type": "Identifier","start": 6,"end": 7,"loc": {"start": {"line": 1,"column": 6,"index": 6},"end": {"line": 1,"column": 7,"index": 7},"identifierName": "x"},"name": "x"},"init": {"type": "BinaryExpression","start": 10,"end": 15,"loc": {"start": {"line": 1,"column": 10,"index": 10},"end": {"line": 1,"column": 15,"index": 15}},"left": {"type": "NumericLiteral","start": 10,"end": 11,"loc": {"start": {"line": 1,"column": 10,"index": 10},"end": {"line": 1,"column": 11,"index": 11}},"extra": {"rawValue": 1,"raw": "1"},"value": 1},"operator": "+","right": {"type": "NumericLiteral","start": 14,"end": 15,"loc": {"start": {"line": 1,"column": 14,"index": 14},"end": {"line": 1,"column": 15,"index": 15}},"extra": {"rawValue": 2,"raw": "2"},"value": 2}}}],"kind": "const"}],"directives": []},"comments": []
}
const code = gennerator(ast, {}, '');
console.log(code.code)