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phab/webroot/rsrc/externals/javelin/core/util.js
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util.js
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/**
* Javelin utility functions.
*
* @provides javelin-util
*
* @javelin-installs JX.$E
* @javelin-installs JX.$A
* @javelin-installs JX.$AX
* @javelin-installs JX.isArray
* @javelin-installs JX.copy
* @javelin-installs JX.bind
* @javelin-installs JX.bag
* @javelin-installs JX.keys
* @javelin-installs JX.log
* @javelin-installs JX.id
* @javelin-installs JX.now
*
* @javelin
*/
/**
* Throw an exception and attach the caller data in the exception.
*
* @param string Exception message.
*
* @group util
*/
JX.$E = function(message) {
var e = new Error(message);
var caller_fn = JX.$E.caller;
if (caller_fn) {
e.caller_fn = caller_fn.caller;
}
throw e;
};
/**
* Convert an array-like object (usually ##arguments##) into a real Array. An
* "array-like object" is something with a ##length## property and numerical
* keys. The most common use for this is to let you call Array functions on the
* magical ##arguments## object.
*
* JX.$A(arguments).slice(1);
*
* @param obj Array, or array-like object.
* @return Array Actual array.
*
* @group util
*/
JX.$A = function(mysterious_arraylike_object) {
// NOTE: This avoids the Array.slice() trick because some bizarre COM object
// I dug up somewhere was freaking out when I tried to do it and it made me
// very upset, so do not replace this with Array.slice() cleverness.
var r = [];
for (var ii = 0; ii < mysterious_arraylike_object.length; ii++) {
r.push(mysterious_arraylike_object[ii]);
}
return r;
};
/**
* Cast a value into an array, by wrapping scalars into singletons. If the
* argument is an array, it is returned unmodified. If it is a scalar, an array
* with a single element is returned. For example:
*
* JX.$AX([3]); // Returns [3].
* JX.$AX(3); // Returns [3].
*
* Note that this function uses a @{function:JX.isArray} check whether or not
* the argument is an array, so you may need to convert array-like objects (such
* as ##arguments##) into real arrays with @{function:JX.$A}.
*
* This function is mostly useful to create methods which accept either a
* value or a list of values.
*
* @param wild Scalar or Array.
* @return Array If the argument was a scalar, an Array with the argument as
* its only element. Otherwise, the original Array.
*
* @group util
*/
JX.$AX = function(maybe_scalar) {
return JX.isArray(maybe_scalar) ? maybe_scalar : [maybe_scalar];
};
/**
* Checks whether a value is an array.
*
* JX.isArray(['an', 'array']); // Returns true.
* JX.isArray('Not an Array'); // Returns false.
*
* @param wild Any value.
* @return bool true if the argument is an array, false otherwise.
*
* @group util
*/
JX.isArray = Array.isArray || function(maybe_array) {
return Object.prototype.toString.call(maybe_array) == '[object Array]';
};
/**
* Copy properties from one object to another. If properties already exist, they
* are overwritten.
*
* var cat = {
* ears: 'clean',
* paws: 'clean',
* nose: 'DIRTY OH NOES'
* };
* var more = {
* nose: 'clean',
* tail: 'clean'
* };
*
* JX.copy(cat, more);
*
* // cat is now:
* // {
* // ears: 'clean',
* // paws: 'clean',
* // nose: 'clean',
* // tail: 'clean'
* // }
*
* NOTE: This function does not copy the ##toString## property or anything else
* which isn't enumerable or is somehow magic or just doesn't work. But it's
* usually what you want.
*
* @param obj Destination object, which properties should be copied to.
* @param obj Source object, which properties should be copied from.
* @return obj Modified destination object.
*
* @group util
*/
JX.copy = function(copy_dst, copy_src) {
for (var k in copy_src) {
copy_dst[k] = copy_src[k];
}
return copy_dst;
};
/**
* Create a function which invokes another function with a bound context and
* arguments (i.e., partial function application) when called; king of all
* functions.
*
* Bind performs context binding (letting you select what the value of ##this##
* will be when a function is invoked) and partial function application (letting
* you create some function which calls another one with bound arguments).
*
* = Context Binding =
*
* Normally, when you call ##obj.method()##, the magic ##this## object will be
* the ##obj## you invoked the method from. This can be undesirable when you
* need to pass a callback to another function. For instance:
*
* COUNTEREXAMPLE
* var dog = new JX.Dog();
* dog.barkNow(); // Makes the dog bark.
*
* JX.Stratcom.listen('click', 'bark', dog.barkNow); // Does not work!
*
* This doesn't work because ##this## is ##window## when the function is
* later invoked; @{method:JX.Stratcom.listen} does not know about the context
* object ##dog##. The solution is to pass a function with a bound context
* object:
*
* var dog = new JX.Dog();
* var bound_function = JX.bind(dog, dog.barkNow);
*
* JX.Stratcom.listen('click', 'bark', bound_function);
*
* ##bound_function## is a function with ##dog## bound as ##this##; ##this##
* will always be ##dog## when the function is called, no matter what
* property chain it is invoked from.
*
* You can also pass ##null## as the context argument to implicitly bind
* ##window##.
*
* = Partial Function Application =
*
* @{function:JX.bind} also performs partial function application, which allows
* you to bind one or more arguments to a function. For instance, if we have a
* simple function which adds two numbers:
*
* function add(a, b) { return a + b; }
* add(3, 4); // 7
*
* Suppose we want a new function, like this:
*
* function add3(b) { return 3 + b; }
* add3(4); // 7
*
* Instead of doing this, we can define ##add3()## in terms of ##add()## by
* binding the value ##3## to the ##a## argument:
*
* var add3_bound = JX.bind(null, add, 3);
* add3_bound(4); // 7
*
* Zero or more arguments may be bound in this way. This is particularly useful
* when using closures in a loop:
*
* COUNTEREXAMPLE
* for (var ii = 0; ii < button_list.length; ii++) {
* button_list[ii].onclick = function() {
* JX.log('You clicked button number '+ii+'!'); // Fails!
* };
* }
*
* This doesn't work; all the buttons report the highest number when clicked.
* This is because the local ##ii## is captured by the closure. Instead, bind
* the current value of ##ii##:
*
* var func = function(button_num) {
* JX.log('You clicked button number '+button_num+'!');
* }
* for (var ii = 0; ii < button_list.length; ii++) {
* button_list[ii].onclick = JX.bind(null, func, ii);
* }
*
* @param obj|null Context object to bind as ##this##.
* @param function Function to bind context and arguments to.
* @param ... Zero or more arguments to bind.
* @return function New function which invokes the original function with
* bound context and arguments when called.
*
* @group util
*/
JX.bind = function(context, func, more) {
if (__DEV__) {
if (typeof func != 'function') {
JX.$E(
'JX.bind(context, <yuck>, ...): '+
'Attempting to bind something that is not a function.');
}
}
var bound = JX.$A(arguments).slice(2);
if (func.bind) {
return func.bind.apply(func, [context].concat(bound));
}
return function() {
return func.apply(context || window, bound.concat(JX.$A(arguments)));
};
};
/**
* "Bag of holding"; function that does nothing. Primarily, it's used as a
* placeholder when you want something to be callable but don't want it to
* actually have an effect.
*
* @return void
*
* @group util
*/
JX.bag = function() {
// \o\ \o/ /o/ woo dance party
};
/**
* Convert an object's keys into a list. For example:
*
* JX.keys({sun: 1, moon: 1, stars: 1}); // Returns: ['sun', 'moon', 'stars']
*
* @param obj Object to retrieve keys from.
* @return list List of keys.
*
* @group util
*/
JX.keys = Object.keys || function(obj) {
var r = [];
for (var k in obj) {
r.push(k);
}
return r;
};
/**
* Identity function; returns the argument unmodified. This is primarily useful
* as a placeholder for some callback which may transform its argument.
*
* @param wild Any value.
* @return wild The passed argument.
*
* @group util
*/
JX.id = function(any) {
return any;
};
JX.log = JX.bag;
if (__DEV__) {
if (!window.console || !window.console.log) {
if (window.opera && window.opera.postError) {
window.console = {log: function(m) { window.opera.postError(m); }};
} else {
window.console = {log: function(m) { }};
}
}
/**
* Print a message to the browser debugging console (like Firebug). This
* method exists only in ##__DEV__##.
*
* @param string Message to print to the browser debugging console.
* @return void
*
* @group util
*/
JX.log = function(message) {
window.console.log(message);
};
window.alert = (function(native_alert) {
var recent_alerts = [];
var in_alert = false;
return function(msg) {
if (in_alert) {
JX.log(
'alert(...): '+
'discarded reentrant alert.');
return;
}
in_alert = true;
recent_alerts.push(JX.now());
if (recent_alerts.length > 3) {
recent_alerts.splice(0, recent_alerts.length - 3);
}
if (recent_alerts.length >= 3 &&
(recent_alerts[recent_alerts.length - 1] - recent_alerts[0]) < 5000) {
if (confirm(msg + "\n\nLots of alert()s recently. Kill them?")) {
window.alert = JX.bag;
}
} else {
// Note that we can't .apply() the IE6 version of this "function".
native_alert(msg);
}
in_alert = false;
};
})(window.alert);
}
/**
* Date.now is the fastest timestamp function, but isn't supported by every
* browser. This gives the fastest version the environment can support.
* The wrapper function makes the getTime call even slower, but benchmarking
* shows it to be a marginal perf loss. Considering how small of a perf
* difference this makes overall, it's not really a big deal. The primary
* reason for this is to avoid hacky "just think of the byte savings" JS
* like +new Date() that has an unclear outcome for the unexposed.
*
* @return Int A Unix timestamp of the current time on the local machine
*/
JX.now = (Date.now || function() { return new Date().getTime(); });
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