Inspect the names/values of arguments in the definition/execution of a JavaScript function

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北海茫月

I\'m looking to do the equivalent of Python\'s inspect.getargspec() in Javascript.

I do know that you can get the arguments list from a Jav

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鱼传尺愫

2020-11-30 11:34

Sightly improved version of Jonathan Fingland's answer:

// Utility function to extract arg name-value pairs
function getArgs(args) {
    var argsObj = {};

    var argList = /\(([^)]*)/.exec(args.callee)[1];
    var argCnt = 0;
    var tokens;

    while (tokens = /\s*([^,]+)/g.exec(argList)) {
        argsObj[tokens[1]] = args[argCnt++];
    }

    return argsObj;
}

// Test subject
function add(number1, number2) {
    var args = getArgs(arguments);
    alert(args.toSource()); // ({number1:3,number2:4})
}

// Invoke test subject
add(3, 4);

Note: This only works on browsers that support arguments.callee.

(Also posted at How to get function parameter names/values dynamically from javascript)

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小鲜肉

2020-11-30 11:36
While I can't see any good reason for this,
```
var reg = /\(([\s\S]*?)\)/;
var params = reg.exec(func);
if (params) 
     var param_names = params[1].split(',');
```
assuming func is the name of your function
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故里飘歌

2020-11-30 11:39

here a small nodejs module for that.

https://github.com/kilianc/node-introspect

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北荒

2020-11-30 11:40

The following function will return an array of parameter names of any function passed in.

function getParamNames(func) {
    var funStr = func.toString();
    return funStr.slice(funStr.indexOf('(')+1, funStr.indexOf(')')).match(/([^\s,]+)/g);
}

Example usage:

getParamNames(getParamNames) // returns ['func']
getParamNames(function (a,b,c,d){}) // returns ['a','b','c','d']

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逝去的感伤

2020-11-30 11:59

Here's a version that uses higher order functions. The only thing I don't like about it is that you have to specify parameters as members of an array. But at least they only have to be specified once.

<!DOCTYPE html>

<html>
<head>
<meta charset="UTF-8">
<title></title>
<script type="text/javascript">
var withNamedParams = function(params, lambda) {
    return function() {
        var named = {};
        var max   = arguments.length;

        for (var i=0; i<max; i++) {
            named[params[i]] = arguments[i];
        }

        return lambda(named);
    };
};

var foo = withNamedParams(["a", "b", "c"], function(params) {
    for (var param in params) {
        alert(param + ": " + params[param]);
    }
});

foo(1, 2, 3);
</script>
</head>
<body>

</body>
</html>

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