How to use the AssignmentPattern function from estraverse

estraverse.AssignmentPattern is a type of AST node in the Estraverse library that represents a default value for a function parameter in JavaScript.

How does estraverse.AssignmentPattern work?

Sure! estraverse.AssignmentPattern is a type of AST node in the Estraverse library that represents a default value for a function parameter in JavaScript. In JavaScript, you can define a function with default parameter values. If a function call omits an argument corresponding to a default parameter, the default value is used instead. estraverse.AssignmentPattern is used to represent the default value expression in the function parameter. For example, consider the following function: javascript Copy code {{{{{{{ function greet(name = 'world') { console.log(`Hello, ${name}!`); } The function greet has a default parameter name that is set to the string 'world'. If the function is called with no arguments, the default value 'world' is used. The AST representation of the function greet includes an AssignmentPattern node representing the default value 'world'. This node has a left property that represents the function parameter (name), and a right property that represents the default value expression ('world'). estraverse.AssignmentPattern is just one of several types of AST nodes available in the Estraverse library. Other node types include VariableDeclaration, FunctionDeclaration, and Literal. Estraverse provides a way to traverse and manipulate the AST of a JavaScript program.

Ai Example

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
const estraverse = require("estraverse");
const { parseScript } = require("esprima");

const code =
  'function greet(name = "world") { console.log(`Hello, ${name}!`); }';
const ast = parseScript(code);

estraverse.traverse(ast, {
  enter(node) {
    if (node.type === "AssignmentPattern") {
      console.log(
        `Parameter '${node.left.name}' has default value '${node.right.value}'`
      );
    }
  },
});

In this example, we first define a string code containing a function with a default parameter value. We use the esprima library to parse the string into an abstract syntax tree (AST). We then use the estraverse library to traverse the AST and extract information about the default parameter values. We call the estraverse.traverse() method, passing in the AST and an object with an enter() method that is called for each AST node. In the enter() method, we check if the node type is 'AssignmentPattern', which represents a default parameter value. We log the name of the parameter and its default value to the console using console.log(). Running this code produces the output: sql Copy code