Question

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

When debugging javascript, I often have code like this:

function doSomething(a,b,c) {
    console.log(a,b,c);

    //function contents here
    //...
}

This results in a line in the console like this:

0.0010719847172334315 0.002392010391772366 -2.764548758273147e-7

Which is hard to read. I want to have output like this:

a: 0.0010719847172334315, b: 0.002392010391772366, c: -2.764548758273147e-7

Is this possible to do? I don’t think it is possible to do in many languages. However, I don’t know javascript very well, and it seems like a language where it is possible to do clever things like this.

Answer 1

You can do something like this by taking in a parameter object and iterating over it:

function doSomething(options) {
    var i, parameterString = [];
    for (i in options) {
        if (!options.hasOwnProperty(i)) continue;
        parameterString.push(i + ': ' + options[i]);
    }
    console.log(parameterString.join(', '));

    //function contents here
    //...
}

// Invoke like this:
var result = doSomething({a: 'a', b: 'b', c: 'c'});

Note that most of the cruft is due to you wanting to log the parameters on one line; in some other cases (such as logging one per line), you can simply call console.log on each of the individual strings and not bother with the array or the string join.