How to get method name from JavaScript file - javascript

I have a JavaScript file with many methods defined in it. Is there any way to know how many methods are in that file & what are the names of methods?

Is there any way to know that how many methods are there in Java
Script & what is the names of method?
Read the source or the documentation (if there is any).
If you're looking for some kind of "list avaialble methods" function, there isn't one. Writing one would be the equivalent of writing a javascript parser and perhaps even compiler.
Good luck with that. :-)

While, in theory, you could try to find everything that matched the pattern:
function <name>(
You'd be missing out on a lot of other types of functions. See, Functions are really just objects in JavaScript. They can be assigned, shared, modified, and moved around. So, you'd also have to find these:
var <name> = function() {}
And these:
function returnFunc() {
return function() {...}
}
var <name> = returnFunc();
As well as these:
obj.member = new Function();
And a nearly infinite variety of similar function definitions.
So, the answer is, most likely you can't. Unless the code is extremely narrowly constructed.

The short answer is "no".
The long answer is that if the JS file is your JS file, i.e., you control the content, then there are several ways that you can structure the code that will let you obtain a count or list of function names. Obviously that won't help you with other people's code. Apologies if you already know all of this, but just in case you don't: it's generally a good idea to wrap all of your "library" functions up as properties of a single object, something like this:
var myFunctionLibrary = {
doSomething : function() {},
somethingElse : function() {},
nonFunctionProperty : "test",
// etc.
}
This creates a single global variable called myFunctionLibrary, which is an object with properties that are references to functions. (Note: there are several other ways to achieve a similar effect, ways that I prefer over this way, but this seems simplest for purposes of this explanation.) You then access the functions by saying:
myFunctionLibrary.doSomething();
// or
myFunctionLibrary["doSomething"]();
Because all of your functions are then contained in a specific object you can iterate over them like any other object:
var funcCount = 0;
var propCount = 0;
for (fn in myFunctionLibrary) {
if (typeof myFunctionLibrary[fn] === "function"){
funcCount++;
alert("Function name: " + fn);
} else {
propCount++;
}
}
alert("There are " + funcCount + " functions available, and "
+ propcount + " other properties.");
The main advantage, though, is that you don't have to worry about your functions potentially having the same names as functions in some other library that you want to use.

Write a program to load your file into Rhino, and then inspect the dictionaries and see what you have.

Related

running code in another function's scope (JavaScript)

So I'm working on a sort of JavaScript framework, just some utility things for myself to use in future projects, and I want to make a data binding system.
The first method I used was objects, and the code would just loop through the specified html element and look for occurences of {{key}} in the markup and then look for that key in the object and replace it that way in the HTML.
For example, if you had <div>{{name}} is a cool guy</div> in the HTML and had {name:"joseph"} in the JS then the final product would be displayed on screen as 'joseph is a cool guy'.
However, I decided later to change my method and instead the framework would except a function. So instead of {name:"joseph"} you would give it function(){ var name = "joseph" }.
This obviously looks better and gives a lot better functionality.
I changed the processing function so instead of looking for the key/value pair to replace the {{key}}, it just uses eval on the variable to gets its value.
My problem lies here: How do I run my search/replace code INSIDE the scope of the function the user passes.
If the user defines variables within that function, their values will not be available anywhere else due to scope issues.
I've tried using Function.toString() to actually modify the source code of the function, but nothing's working and it's all very complicated.
(The issues are not due to the actual solution, I think that Function.toString() might work, but due to my implementation. I keep getting errors)
So... What is the best way to run arbitrary code in the scope of another function?
Critera:
Obviously, I can't modify the function because the user is passing it in. (you can't just tell me to add the search/replace code to the bottom of the function)
The variables must stay in the local scope of the function. (no cheating by using window.name = "joseph" or anything)
I am also aware of how terrible eval is so any suggestions as to get it to work are greatly appreciated. Thanks!
Code:
function process(html) {
var vars = html.match( /({{)[^{}]*(}})/g )
// vars = ['{{variable}}', '{{anotherVariable}}']
var names = vars.map( function(x){ return x.replace("{{", "").replace("}}", "") } )
// names = ['variable', 'anotherVariable]
obj = {}
for (var i = 0; i < names.length; i++) {
obj[names[i]] = eval(names[i])
}
for (var p in obj) {
html = html.replace(new RegExp('{{'+p+'}}','g'), obj[p]);
}
return html
}
You should go back to your first method with the object, it's much better. You can still pass a function, but the function should return an object:
function () {
return { name: 'joseph' }
}

Get Javascript function name

Is there a way to obtain function's name from outside of it?
Lets say there is a js script on web page that we cannot modificate, just read. The script contains object, which contains objects and functions. Lets say that we want to find function named "HelloWorld".
With firebug, we loop through these objects and methods with a script, which looks something like this
// Parameter is target object.
function getFunctionNames(obj) {
// For each objects / functions
for (var id in obj) {
// Focus only on functions
if (typeof(obj[id]) == "function") {
// Get name of the function.
// console.log("Function: " + obj[id].toString());
// Code above returns a block of code without the name. Example output:
// Function: function(name) { alert("Hello World! Hello " + name + "!"); }
//
// Expected output would be
// Function: HelloWorld
}
}
}
obj[id].toString() returns a block of code instead of a name.
obj[id].name returns an empty string. Anonymous function(?).
I cannot use arguments.callee.name because I cannot modify the target code.
I could just browse objects and functions in firebug or just read source code, but I'm looking a way to do it with Javascript.
Edit
For real world example, head to Youtube and try to get the name of function "setMsg()" from "yt" object via Javascript.
Edit2
Accepting Simon's answer for being kinda closest what I was looking for. It appears that I was seeking variable name, rather than function name. While answer didn't help me on original problem, it surely answered to original question. Paul Draper's comments helped me to right direction.
Thanks!
Use obj.name
Note that arguments.callee returns a function. name is property on every function (though it's empty for anonymous functions), so that's why arguments.callee.name works.
This works for webkit (Chrome and Safari), Firefox, and possibly others. It does not work for IE: function.name not supported in IE.
As mentioned, the function doesn't have any intrinsic name other than the "" it gets from being an anonymous function. Some browsers (Firefox, probably Chrome, maybe others) do however perform some limited form of static analysis to figure out names of declared functions, to help with error stack traces. You can get to it in an relatively cross-browser way by getting setMsg to throw an exception and then parse exc.stack:
// cheat with .% in Firebug; there might be other ways of doing this, I dunno:
yt.setMsg.%m.za.__defineSetter__('a', function() { throw new Error(); });
try { yt.setMsg('a', 'a'); }
catch(e) { alert(e.stack.split('\n')[2].split('#')[0]); }
... On the other hand, this is a pretty terrible hack and dependent on the actual function involved (and if you know the function, you probably know its name already). It does work a bit more reliably when done from inside the function.
If you restrict yourself to just Firefox and are doing this for debug purposes, there are better ways of getting to it. Set devtools.chrome.enabled to true in about:config, open a Scratchpad (Shift+F4), set it to environment: browser, and run the following:
Components.utils.import("resource://gre/modules/jsdebugger.jsm");
window.addDebuggerToGlobal(window);
dbg = new Debugger();
dw = dbg.addDebuggee(content);
f = content.wrappedJSObject.yt.setMsg;
name = dw.makeDebuggeeValue(f).displayName;
dbg.removeDebuggee(content);
alert(name);
In both cases, you will note that it alerts "m.ya" instead of "setMsg", and indeed this is because the function was originally declared as m.ya = function() { ...; }. There is no reason why "setMsg" would be a preferable name, from the point of the browser.

How to serialize an object in JavaScript?

For example I have class:
function Test() {
}
Test.prototype = {
'setTest' : function(test) {
this.test = test;
}
}
var test = new Test();
Test.setTest('test');
I want to save object test in database.
How to serialize object test to string? (methods, variables, etc)
Simple with json
JSON.stringify( test );
In this case, for the question you're asking, there really isn't a way to do what you want. The problem with your request lies in "serializing everything attached to the object, including functions".
Serialization normally only occurs for data, because executables are usually machine bound, in that they are compiled for a given machine, based on certain characteristics. Now, it's reasonable to say that javascript functions just require a javascript interpreter, because javascript is write-once, run-everywhere. But when people write serializers, because all serializers tend to work the same, we write them for data only. In this case, the industry standard is JSON, which is an object-data only serializer.
There are three solutions that avail themselves to you at this point:
Write your own serialier/deserializer that encapsulates functions. This can be tricky, because not all javascript engines will give you access to the source.
Write your own re-loading mechanism that generates a specific new initialized type on each restore, and save the typename as one of the properties on serialization. That way the initialization of each variable gives you the methods, and then merging with the data gives you the complete object.
Store each function as a string and eval it on the fly as you need it. This is incredibly tricky, and is quite prone to errors. I can think of no case where this becomes helpful, because it's quite fragile. However, it is an option, and cannot be overlooked.
I know that 3 is a sub-answer for 1, so you can consider it that there are only two useful answers.
I know that superficially this works on Chrome and IE9, so it should work everywhere the majority of users are likely to use it:
var abc = function(thing) { return thing; }
abc.toString();
// gives "function(thing) { return thing; }" on the command line
So you can certainly serialize the methods as strings in place of the actual method, but you're going to need to create a duplicate object so you can capture every element on the source object (I think, rather than replacing them in place).
Hopefully this helps you think about the problem some more, and maybe to realize you don't need to serialize the methods (nobody ever does that I know of, not reasonably).
The best way to do this is to write your own serialize method which creates a JSON object with attributes, based on your getters. Normally you define a getter per attribute. So it should work for most cases (so you don't have to define a serialize method for each class).
function serialize(obj) {
var serialized = {};
for(var prop in obj) {
if (obj.hasOwnProperty(prop) && typeof obj[prop] == 'function') {
if (/^get.*/.test(prop)) {
var value = obj[prop]();
var name = prop.replace('get', '');
if (typeof value === 'object') {
serialized[name] = this.serialize(value);
continue;
}
serialized[name] = value;
}
}
}
return serialized;
};
To reset your attribute values back to the class you have two options:
Create a function in your class which creates a valid object instance based on the serialized JSON.
Create a unserialize method and map the JSON with your class using the setters.
Example:
function unserialize(obj, emptyClass) {
// Check emptyClass for setters and map the data from obj to it.
return 'class instance';
}
Typically, you'd do this with JSON, which is widely supported across browsers/languages/libraries/etc. The only hangup is that JSON does not support functions – but do you really need to serialize those?
I've had to support functionality similar to this before. I ended up saving the name of the function as a string and serializing it as JSON. Then when I come back to the client, I execute the function using a helper like the one posted in this question.
If anyone has a better way to solve this problem, I'd want to see it!
I recently had to find a solution for this problem. I'm sure it can be improved upon.
First I created a module for instantiating the "serialisable" object.
function MyObj(serialised){
this.val = "";
if(serialised){
var unserialised = JSON.parse(serialised);
for (var i in unserialised) {
this[i] = unserialised[i];
}
}
}
MyObj.prototype.myMethod = function () { return this.val;};
module.exports = MyObj;
you of course have to consider error handling and other validations.

Obfuscate javascript properties?

I've recently tested UglifyJS and YUI Compressor and noticed something odd.
Both minifiers don't seem to change the names of object properties, only the names of variables and functions.
for instance if I have the following code:
var objName = {first:2, second:4};
alert(objName.first + " " + objName.second);
the names first and second remain unchanged in the minified version.
Why is that?
Since in javascript a new scope is created in a function, you can scope your code in an immediately invoked function.
// scoped
(function() {
var objName = {first:2, second:4};
alert(objName.first + " " + objName.second);
})();
Then using Google's Closure Compiler, if you turn on the "Advanced" optimization it will see that the properties are only used locally, and will obfuscate them.
// result
var a={a:2,b:4};alert(a.a+" "+a.b);
It's because it doesn't know where the object is going to be used. It could be used externally by other code and you wouldn't want your other code to have to change whenever you obfuscate it.
Edit So basically, it's like that to prevent obfuscation from breaking external/internal references to properties that may not be possible to figure out while obfuscating.
Since there are no well defined scoping rules around objects in JavaScript it's impossible to obfuscate the names in a way that is guaranteed to be correct.
For example, if you had the following function:
function f() {
return { first: 'foo', second: 'bar' };
}
In order to obfuscate the property names you would have to nail down all the places that f is called from. Since functions are first-class in JavaScript they can be assigned and passed around in arbitrary ways making it impossible to pin down where f is referenced without actually running the program.
Additionally, JavaScript doesn't have any way for you to specify intent around what's public API and what isn't. Even if the minimizer could reliably determine where the function is called from in the code you give it, there would be no way for it to make the same changes to code that it hasn't seen.
I guess that's because the minifiers would break the object properties. Consider this:
function getProp(ob,name) {
return ob[name];
}
var objName = {first: 2, second: 4};
var prop = getProp(objName, "second");
There's no way for the minifier to know the string literal "second" being an object property. The minified code could look like this then:
function a(b,c){return b[c]}var d={p1:2,p2:4};var e=a(d,"second")
Broken now.
The latest release of uglify (today) has object property mangling, see v2.4.19. It also supports reserved files for excluding both object properties and variables that you don't want mangled. Check it out.
The only public tool so far to obfuscate property and function names (afaik) is the Closure Compiler's Advanced mode. There are a lot of limitations and restrictions, but the end result is generally worth it.
As a passing note: the Dojo Toolkit is compatible (with some minor modifications) with the Closure Compiler in Advanced mode -- arguably the only large-scale public JavaScript library that can be fully obfuscated. So if you are looking at obfuscation to protect your IP, you should look into using Dojo for the task.
http://dojo-toolkit.33424.n3.nabble.com/file/n2636749/Using_the_Dojo_Toolkit_with_the_Closure_Compiler.pdf?by-user=t
Stephen
What about doing something like:
// scoped
(function() {
var objName = {first:2, second:4};
var vA = 'first';
var vB = 'second';
alert(objName[vA] + " " + objName[vB]);
})();
Once objName.first and/or objName.second are referenced enough times, this technique will start to save characters. I can't think of any reason that wouldn't work, but I can't find any minifiers that do it.

How to fix jslint error 'Don't make functions within a loop.'?

I am working on making all of our JS code pass through jslint, sometimes with a lot of tweaking with the options to get legacy code pass for now on with the intention to fix it properly later.
There is one thing that jslint complains about that I do not have a workround for. That is when using constructs like this, we get the error 'Don't make functions within a loop.'
for (prop in newObject) {
// Check if we're overwriting an existing function
if (typeof newObject[prop] === "function" && typeof _super[prop] === "function" &&
fnTest.test(newObject[prop])) {
prototype[prop] = (function(name, func) {
return function() {
var result, old_super;
old_super = this._super;
this._super = _super[name];
result = func.apply(this, arguments);
this._super = old_super;
return result;
};
})(prop, newObject[prop]);
}
}
This loop is part of a JS implementation of classical inheritance where classes that extend existing classes retain the super property of the extended class when invoking a member of the extended class.
Just to clarify, the implementation above is inspired by this blog post by John Resig.
But we also have other instances of functions created within a loop.
The only workaround so far is to exclude these JS files from jslint, but we would like to use jslint for code validation and syntax checking as part of our continuous integration and build workflow.
Is there a better way to implement functionality like this or is there a way to tweak code like this through jslint?
Douglas Crockford has a new idiomatic way of achieving the above - his old technique was to use an inner function to bind the variables, but the new technique uses a function maker. See slide 74 in the slides to his "Function the Ultimate" talk. [This slideshare no longer exists]
For the lazy, here is the code:
function make_handler(div_id) {
return function () {
alert(div_id);
};
}
for (i ...) {
div_id = divs[i].id;
divs[i].onclick = make_handler(div_id);
}
(I just stumbled on this questions many months after it was posted...)
If you make a function in a loop, an instance of a function is created for each iteration of the loop. Unless the function that is being made is in fact different for each iteration, then use the method of putting the function generator outside the loop -- doing so isn't just Crockery, it lets others who read your code know that this was your intent.
If the function is actually the same function being assigned to different values in an iteration (or objects produced in an iteration), then instead you need to assign the function to a named variable, and use that singular instance of the function in assignment within the loop:
handler = function (div_id) {
return function() { alert(div_id); }
}
for (i ...) {
div_id = divs[i].id;
divs[i].onclick = handler(div_id);
}
Greater commentary/discussion about this was made by others smarter than me when I posed a similar question here on Stack Overflow:
JSlint error 'Don't make functions within a loop.' leads to question about Javascript itself
As for JSLint:
Yes, it is dogmatic and idiomatic. That said, it is usually "right" -- I discover that many many people who vocalize negatively about JSLint actually don't understand (the subtleties of) Javascript, which are many and obtuse.
Literally, get around the problem by doing the following:
Create a .jshintrc file
Add the following line to your .jshintrc file
{"loopfunc" : true, // tolerate functions being defined in loops }
JSLint is only a guide, you don't always have to adhere to the rules. The thing is, you're not creating functions in a loop in the sense that it's referring to. You only create your classes once in your application, not over and over again.
If you are using JQuery, you might want to do something like this in a loop:
for (var i = 0; i < 100; i++) {
$("#button").click(function() {
alert(i);
});
}
To satisfy JSLint, one way to work around this is (in JQuery 1.4.3+) to use the additional handler data argument to .click():
function new_function(e) {
var data = e.data; // from handler
alert(data); // do whatever
}
for (var i = 0; i < 100; i++) {
$("#button").click(i, new_function);
}
Just move your:
(function (name, func) {...})()
block out of the loop and assign it to a variable, like:
var makeFn = function(name, func){...};
Then in the loop have:
prototype[prop] = makeFn(...)

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