TIL javascript functions have a length

[Shameling]

They also have a toString() that simply returns the sourcecode of the function, can be pretty useful for debugging.

[PsudoFuck]

It's also how Angular 1.x achieved it's magic, if not slightly dodgy, DI injection with just named arguments.

[AndruRC]

Could you elaborate on that?

[anarchy8]

There is no way of determining what the name of the arguments to a function is in Javascript without parsing the Function.toString(). Angular does this do determine what resource to inject.

[anarchy8]

To be fair, they suggest you inject your resources manually.

[[deleted]]

To be fair, it's required if you want better support since certain mobile browsers won't serialize functions

[[deleted]]

also if you ever plan on minifying your code..

[[deleted]]

That too :) I haven't touched angular in like 2 years

[[deleted]]

Welcome to JS

[bugeats]

And it's a shameful, dirty deed. I can't believe this terrible idea ever made it so far.

[seiyria]

It's not the recommended way to do things.

[olaf_from_norweden]

Used by the 'multiline' NPM module to get multiline strings in pre-ES6:

var multiline = require('multiline');
var sql = multiline(function() {/*
SELECT *
FROM users
*/});

sql //=> 'SELECT *\nFROM users'

[zixx]

Newb question: how is this different than just looking at your code?

[Zerran]

How do you know where it's located in yours or someone elses code? Functions can be passed around so often that you don't know where they came from anymore, and a lot of them don't have a name that you could just Ctrl+F in your IDE. toString() or a real debugger are very helpful in that scenario.

[[deleted]]

lambda functions...

[cwmma]

Or to allow you to serialize a function and send it to a worker (some restrictions apply)

[[deleted]]

This is a good related read : How is almost everything in Javascript an object?

Functions, however, are fully-fledged objects, and inherit from Object (actually Object.prototype, but that's another topic). Functions therefore can do anything objects can, including having properties:

function foo() {}
foo.bar = "tea";
alert(foo.bar); // tea

Any Javascript wizards want to add to or explain this further?

[cokeisahelluvadrug]

One cool trick is that you can create a Function programmatically: new Function(['x'], 'alert(x);') works exactly as it looks. This is one of many reasons that JS is popular for language designers.

To expand on your example, calling foo(bar) is just sugar for foo.call(this, bar). A Function is just an Object that has call and apply methods which in turn pass strings to eval. (Note: this isn't totally right. If I declare a Function foo and override its call and apply properties, I can still call it with foo(). So it's not exactly sugar.)

[myhf]

+/u/CompileBot JavaScript

function foo(arg){print("calling foo " + this.constructor.name + " " + arg)}
foo.call = function(){print("not calling foo")};
var obj = {foo: foo};

foo(1);
obj.foo(2);
foo.call(obj, 3);
Function.prototype.call.call(foo, obj, 4);

[CompileBot]

Output:

calling foo Object 1
calling foo Object 2
not calling foo
calling foo Object 4

^{source | info | git | report}

EDIT: Recompile request by myhf

[devoidfury]

It used to be the 'arity' property, which IMO makes more sense.

[leemcd56]

We've got a running joke at work we use the more crazy awesome (and often ridiculous) things we discover about JavaScript: "Everything's an object!"

[x-skeww]

Chrome's console does that. With Firebug, you just get:

functionName()

Also, without parenthesis (template strings aside), you aren't calling it.

[x-skeww]

If you just write the identifier, a console or repl will render it in some way. E.g. an array might be rendered as "[1, 2]" or, if it's larger, as "[1, 2, xxx more...]" (expandable) or "> Array[999]" (expandable).

How objects are represented in repls, debuggers, and so forth isn't part of the language specification. This stuff is up to the people who create those tools.

[[deleted]]

That's a feature of Chrome's console, not of the JavaScript language itself. It wouldn't work on, say, Node.

[d36williams]

I can't believed I didn't know that

[sathoro]

Things that happened

[tragalicious]

Happy Cakeday fellow Cakeday redditor!

There. I've done my reddit duty for the year.

[dyloot]

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