How to use the traverse function from @babel/types

Find comprehensive JavaScript @babel/types.traverse code examples handpicked from public code repositorys.

@babel/types.traverse is a function that allows you to traverse the abstract syntax tree (AST) of JavaScript code using a visitor pattern.

parse.js

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  placeholderNames: new Set()
};
const isLegacyRef = {
  value: undefined
};
t.traverse(ast, placeholderVisitorHandler, {
  syntactic,
  legacy,
  isLegacyRef,
  placeholderWhitelist,

+ 26 other calls in file

tree.js

GitHub: tachyla/ds_practice

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 //gets removed when the node has called both currentNode.left & currentNode.right
 //pops recursive call off the call stack
let traverse = (currentNode) => {
     results.push(currentNode.value); //pushes current node into array

     if(currentNode.left) traverse(currentNode.left);
     if(currentNode.right) traverse(currentNode.right);
 }
 traverse(this.root);
 return results;

+ 47 other calls in file

How does @babel/types.traverse work?

@babel/types.traverse is a function that allows you to traverse the abstract syntax tree (AST) of JavaScript code using a visitor pattern. When you call @babel/types.traverse on an AST node, it will recursively traverse the entire tree starting from that node, calling visitor functions that you define along the way. The visitor functions are passed two arguments: the current node being traversed and a state object that you can use to keep track of information across multiple visits. By defining visitor functions for different types of AST nodes, you can manipulate or analyze the code represented by the AST. For example, you could use @babel/types.traverse to modify a piece of code to add instrumentation, or to analyze the code to find potential performance issues. Here's an example of how you could use @babel/types.traverse to modify the AST of a JavaScript function: javascript Copy code {{{{{{{ const babel = require('@babel/core'); const types = require('@babel/types'); const traverse = require('@babel/types').traverse; const code = 'function square(x) { return x * x; }'; const ast = babel.parse(code); traverse(ast, { FunctionDeclaration(path) { // Create a new function call node const logCall = types.expressionStatement( types.callExpression(types.identifier('console.log'), [ types.stringLiteral('calling function') ]) ); // Add the new node to the beginning of the function body path.node.body.body.unshift(logCall); } }); const transformedCode = babel.transformFromAstSync(ast, code); console.log(transformedCode.code); In this example, we use @babel/core to parse a string of JavaScript code into an AST. We then call @babel/types.traverse on the AST and define a visitor function for FunctionDeclaration nodes that adds a console.log statement to the beginning of the function body. Finally, we use @babel/core to transform the modified AST back into JavaScript code, and log the transformed code to the console. By using @babel/types.traverse, we can easily traverse and manipulate the AST of JavaScript code, making it a powerful tool for code transformation and analysis.

js.js

GitHub: Aharonabadi/amphtmlML

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const tree = parse(source, {
  sourceType: 'module',
  plugins: ['jsx'],
});

types.traverse(tree, (node, ancestors) => {
  if (types.isObjectProperty(node)) {
    const {value} = node;
    if (!types.isStringLiteral(value) && !types.isNumericLiteral(value)) {
      return;

Ai Example

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const babel = require("@babel/core");
const types = require("@babel/types");
const traverse = require("@babel/types").traverse;

const code = "function square(x) { return x * x; }";
const ast = babel.parse(code);

traverse(ast, {
  FunctionDeclaration(path) {
    // Create a new function call node
    const logCall = types.expressionStatement(
      types.callExpression(types.identifier("console.log"), [
        types.stringLiteral("calling function"),
      ])
    );

    // Add the new node to the beginning of the function body
    path.node.body.body.unshift(logCall);
  },
});

const transformedCode = babel.transformFromAstSync(ast, code);

console.log(transformedCode.code);

In this example, we use @babel/core to parse a string of JavaScript code into an AST. We then call @babel/types.traverse on the AST and define a visitor function for FunctionDeclaration nodes that adds a console.log statement to the beginning of the function body. Finally, we use @babel/core to transform the modified AST back into JavaScript code, and log the transformed code to the console. By running this code, you should see output that looks something like this: javascript Copy code

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