替换节点

2024年11月10日

柏拉文

越努力，越幸运

一、认识

---

二、语法

---

const replaceWith = (ast, targetNode, newNode) => {
  visit(ast, {
    [targetNode.type]: (node, parent) => {
      if (node === targetNode) {
        for (const key in parent) {
          if (parent.hasOwnProperty(key)) {
            if (Array.isArray(parent[key])) {
              parent[key] = parent[key].map((child) =>
                child === targetNode ? newNode : child
              );
            } else if (parent[key] === targetNode) {
              parent[key] = newNode;
            }
          }
        }
      }
    },
  });
};

三、场景

---

3.1 将 var 替换为 let

const oxcParser = require("oxc-parser");

const { parseAsync } = oxcParser;

const parse = async (sourceCode) => {
  try {
    const result = await parseAsync(sourceCode);
    return result;
  } catch (error) {
    console.error("Error parsing source code:", error);
    return "";
  }
};

const visit = (ast, visitor) => {
  function traverse(node, parent) {
    if (!node || typeof node !== "object") return;

    if (visitor[node.type]) {
      visitor[node.type](node, parent);
    }

    for (const key in node) {
      if (!node.hasOwnProperty(key)) continue;

      const child = node[key];
      if (Array.isArray(child)) {
        child.forEach((c) => traverse(c, node));
      } else if (child && typeof child === "object") {
        traverse(child, node);
      }
    }
  }

  traverse(ast, null);
};

const find = (ast, type) => {
  const nodes = [];
  visit(ast, {
    [type]: (node) => {
      nodes.push(node);
    },
  });
  return nodes;
};

const replaceWith = (ast, targetNode, newNode) => {
  visit(ast, {
    [targetNode.type]: (node, parent) => {
      if (node === targetNode) {
        for (const key in parent) {
          if (parent.hasOwnProperty(key)) {
            if (Array.isArray(parent[key])) {
              parent[key] = parent[key].map((child) =>
                child === targetNode ? newNode : child
              );
            } else if (parent[key] === targetNode) {
              parent[key] = newNode;
            }
          }
        }
      }
    },
  });
};

async function main() {
  const ast = await parse(
    `var a = 1; var b = 2; var c = ()=> { var d = 3; return d;};`
  );

  const variableDeclarations = find(ast, "VariableDeclaration");
  variableDeclarations.forEach((node) => {
    if (node.kind === "var") {
      const newNode = {
        ...node,
        kind: "let",
      };
      replaceWith(ast, node, newNode);
    }
  });

  console.log(JSON.stringify(ast, null, 2));
}

main();