How Can I Retrieve All Locally Scoped Variables in a JavaScript Function?

How Can I Access All In-Scope Variables in JavaScript?

Although it's generally acknowledged that there is no direct method for retrieving all currently in-scope variables in JavaScript, a restricted approach exists for accessing local variables within a function.

To achieve this, convert the function to a string using f '', which yields the function's source code. With the help of a parser like Esprima, parse the function's code and identify local variable declarations.

Specifically, look for objects with the type field set to "VariableDeclaration" in the result. For example, in the function f:

var f = function() {
    var x = 0;
};

Parsing the function's code using Esprima returns the following:

{
    "type": "Program",
    "body": [
        {
            "type": "VariableDeclaration",
            "declarations": [
                {
                    "type": "VariableDeclarator",
                    "id": {
                        "type": "Identifier",
                        "name": "x"
                    },
                    "init": {
                        "type": "Literal",
                        "value": 0,
                        "raw": "0"
                    }
                }
            ],
            "kind": "var"
        }
    ]
}

This method only provides access to variables defined within the function itself. For example, in the following function:

var g = function() {
    var y = 0;
    var f = function() {
        var x = 0;
    };
};

Applying the same approach gives access only to the x variable, not y. To access nested variables, a loop using caller can be employed, but the variable names must be known beforehand.

The above is the detailed content of How Can I Retrieve All Locally Scoped Variables in a JavaScript Function?. For more information, please follow other related articles on the PHP Chinese website!