I execute some function and get a return value. This value could be anything (string, array, object, reference, function). I then pass this result along using JSON.stringify.
Now, the functions and references don't do me much good in the scope they're being delivered to, so the whole "to string, eval" method isn't much use. I'm going to store them in a local array and just pass along an ID to reference them by later. But, I do go ahead and send string data, arrays, and objects (in the "associated array" sense of javascript objects) as those all play very nicely with JSON.stringify.
I'm already using try... JSON.stringify() catch to do this with recursive objects (which JSON.stringify errors on.) But that doesn't account for anything else mentioned above.
What is the most efficient way to check if an value contains a function?
And not
typeof foo === "function"
Because the return might be
["foo", "bar", ["foo", "bar"], function(){...something}]
I don't want to pick apart each individual piece's type either, just return on the whole whether there's ANY functions/objects that cannot be safely stringified. I could probably work out how to loop and check each individual value, but if there's a shortcut or more efficient method someone can think of, I'd like to hear it.
Thanks!
Refining welcome and appreciated!
//your favorite object length checking function could go here
$.objectLength = (function(){
//ie<9
if (typeof Object.keys === "undefined" ){
return function(o){
var count = 0, i;
for (i in o) {
if (o.hasOwnProperty(i)) {
count++;
}
}
return count;
};
//everyone else
} else {
return function(o){
return Object.keys(o).length;
}
}
})();
//comparing our two objects
$.checkMatch = function(a, b){
//if they're not the same length, we're done here. (functions exist, etc)
if (typeof a !== typeof b || typeof a === "object" && typeof b === "object" && a && b && $.objectLength(a) !== $.objectLength(b)){
return false;
//if they are the same length, they may contain deeper objects we need to check.
} else {
var key;
for (key in a){
//make sure it's not prototyped key
if (a.hasOwnProperty(key)){
//if it doesn't exist on the other object
if (!b.hasOwnProperty(key)){
return false;
//if this an object as well
} else if (typeof a[key] === "object"){
//check for a match
if (!$.checkMatch(a[key], b[key])){
return false;
}
//then check if they're not equal (simple values)
} else if (a[key] !== b[key]){
return false
}
}
}
return true;
}
};
//...stuff
//catch recursive objects in parameters
var good = true, sendObject = {"ourobject", "values"}, finalSendObject;
//try to stringify, which rejects infinitely recursive objects
try {
finalSendObject = JSON.stringify(sendObject);
} catch(e){
good = false;
}
//if that passes, try matching the original against the parsed JSON string
if (good && sendObject !== JSON.parse(finalSendObject)){
good = $.checkMatch(sendObject, JSON.parse(finalSendObject));
}
This will not work
But I will leave it up for anyone who thinks of trying it. Working solution coming shortly.
30 seconds later, I figure it out myself.
String it, parse it. If anything changed, it wont be equal to itself.
var checkParse = function(obj){
return obj === JSON.parse(JSON.strigify(obj));
}
Related
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
How do you determine equality for two JavaScript objects?
Object comparison in JavaScript
If I have two arrays or objects and want to compare them, such as
object1 = [
{ shoes:
[ 'loafer', 'penny' ]
},
{ beers:
[ 'budweiser', 'busch' ]
}
]
object2 = [
{ shoes:
[ 'loafer', 'penny' ]
},
{ beers:
[ 'budweiser', 'busch' ]
}
]
object1 == object2 // false
this can be annoying if you're getting a response from a server and trying to see if it's changed
Update:
In response to the comments and worries surrounding the original suggestion (comparing 2 JSON strings), you could use this function:
function compareObjects(o, p)
{
var i,
keysO = Object.keys(o).sort(),
keysP = Object.keys(p).sort();
if (keysO.length !== keysP.length)
return false;//not the same nr of keys
if (keysO.join('') !== keysP.join(''))
return false;//different keys
for (i=0;i<keysO.length;++i)
{
if (o[keysO[i]] instanceof Array)
{
if (!(p[keysO[i]] instanceof Array))
return false;
//if (compareObjects(o[keysO[i]], p[keysO[i]] === false) return false
//would work, too, and perhaps is a better fit, still, this is easy, too
if (p[keysO[i]].sort().join('') !== o[keysO[i]].sort().join(''))
return false;
}
else if (o[keysO[i]] instanceof Date)
{
if (!(p[keysO[i]] instanceof Date))
return false;
if ((''+o[keysO[i]]) !== (''+p[keysO[i]]))
return false;
}
else if (o[keysO[i]] instanceof Function)
{
if (!(p[keysO[i]] instanceof Function))
return false;
//ignore functions, or check them regardless?
}
else if (o[keysO[i]] instanceof Object)
{
if (!(p[keysO[i]] instanceof Object))
return false;
if (o[keysO[i]] === o)
{//self reference?
if (p[keysO[i]] !== p)
return false;
}
else if (compareObjects(o[keysO[i]], p[keysO[i]]) === false)
return false;//WARNING: does not deal with circular refs other than ^^
}
if (o[keysO[i]] !== p[keysO[i]])//change !== to != for loose comparison
return false;//not the same value
}
return true;
}
But in many cases, it needn't be that difficult IMO:
JSON.stringify(object1) === JSON.stringify(object2);
If the stringified objects are the same, their values are alike.
For completeness' sake: JSON simply ignores functions (well, removes them all together). It's meant to represent Data, not functionality.
Attempting to compare 2 objects that contain only functions will result in true:
JSON.stringify({foo: function(){return 1;}}) === JSON.stringify({foo: function(){ return -1;}});
//evaulutes to:
'{}' === '{}'
//is true, of course
For deep-comparison of objects/functions, you'll have to turn to libs or write your own function, and overcome the fact that JS objects are all references, so when comparing o1 === ob2 it'll only return true if both variables point to the same object...
As #a-j pointed out in the comment:
JSON.stringify({a: 1, b: 2}) === JSON.stringify({b: 2, a: 1});
is false, as both stringify calls yield "{"a":1,"b":2}" and "{"b":2,"a":1}" respectively. As to why this is, you need to understand the internals of chrome's V8 engine. I'm not an expert, and without going into too much detail, here's what it boils down to:
Each object that is created, and each time it is modified, V8 creates a new hidden C++ class (sort of). If object X has a property a, and another object has the same property, both these JS objects will reference a hidden class that inherits from a shared hidden class that defines this property a. If two objects all share the same basic properties, then they will all reference the same hidden classes, and JSON.stringify will work exactly the same on both objects. That's a given (More details on V8's internals here, if you're interested).
However, in the example pointed out by a-j, both objects are stringified differently. How come? Well, put simply, these objects never exist at the same time:
JSON.stringify({a: 1, b: 2})
This is a function call, an expression that needs to be resolved to the resulting value before it can be compared to the right-hand operand. The second object literal isn't on the table yet.
The object is stringified, and the exoression is resolved to a string constant. The object literal isn't being referenced anywhere and is flagged for garbage collection.
After this, the right hand operand (the JSON.stringify({b: 2, a: 1}) expression) gets the same treatment.
All fine and dandy, but what also needs to be taken into consideration is that JS engines now are far more sophisticated than they used to be. Again, I'm no V8 expert, but I think its plausible that a-j's snippet is being heavily optimized, in that the code is optimized to:
"{"b":2,"a":1}" === "{"a":1,"b":2}"
Essentially omitting the JSON.stringify calls all together, and just adding quotes in the right places. That is, after all, a lot more efficient.
As an underscore mixin:
in coffee-script:
_.mixin deepEquals: (ar1, ar2) ->
# typeofs should match
return false unless (_.isArray(ar1) and _.isArray(ar2)) or (_.isObject(ar1) and _.isObject(ar2))
#lengths should match
return false if ar1.length != ar2.length
still_matches = true
_fail = -> still_matches = false
_.each ar1, (prop1, n) =>
prop2 = ar2[n]
return if prop1 == prop2
_fail() unless _.deepEquals prop1, prop2
return still_matches
And in javascript:
_.mixin({
deepEquals: function(ar1, ar2) {
var still_matches, _fail,
_this = this;
if (!((_.isArray(ar1) && _.isArray(ar2)) || (_.isObject(ar1) && _.isObject(ar2)))) {
return false;
}
if (ar1.length !== ar2.length) {
return false;
}
still_matches = true;
_fail = function() {
still_matches = false;
};
_.each(ar1, function(prop1, n) {
var prop2;
prop2 = ar2[n];
if (prop1 !== prop2 && !_.deepEquals(prop1, prop2)) {
_fail();
}
});
return still_matches;
}
});
So basically i want to check if my data (which is in JSON Format) has a value which is a primitive. So let's take an Example: I get data that looks like this: {name: Artikel, value: {"ArtNr": 1234}} and i want to check if 1234 is primitive or not. I also want to differentiate if the result is an Array with Primitives in it or an Object. Is that possible?
function isObjectContainingPrimitiveValues(test) {
let values = Object.values(test);
for (let i of values) {
console.log(i);
return (typeof i === 'string' || typeof i === 'number' || typeof i === 'boolean' || typeof i === null || typeof i === undefined);
}
}
UPDATE
So with the awesome help of MaxK i have built a isResultContainingPrimitiveValues() Function which checks my data for Primitive/ Primitive Arrays and or Objects. The following part is the trickiest at least with my understanding. The following Example will hopefully help you understand my problems better.
So my let namesSplit = treeNode.name.split('.'); variable splits the data it gets and has as a result of nameSplit : Artikel,Artnr. Next i defined a key variable let key = namesSplit[0]; which has key : Artikel as a result. Than i define a contextEntry variable let contextEntry = exprData.contextEntry.find(_x => _x.name === key); and has contextEntry : {"name":"Artikel","value":{"ArtNr":123}} as a result. Now i want to check: if there's another split namesSplit.length > 1 check isResultContainingPrimitiveValues(). If it is primitive, throw an error, if it is an object -> get values from it and if it is an array -> get values form there. I know it's a lot but from all the confusing stuff i can't seem to think clear, so i appreciate every help i can get.
You are returning from your function on the first iteration. You should only return false if you found an non-primitive and if you were able to loop over all values you can return true because all values are primitives:
function isObjectContainingPrimitiveValues(testObj) {
let values = Object.values(testObj);
for(let i of values){
if (typeof i === 'object') {
return false;
}
}
return true;
};
Update:
After reading your comment i changed the code to check for arrays with primitives as well. The idea is, to create a new function which only checks if a single value is a primitive.Now if we find an array, we can simply check - with the help
of the arrays some function - if some element, inside the array is not primitive. If so return false,otherwise we do the same checks as before:
function isObjectContainingPrimitiveValues(testObj) {
let values = Object.values(testObj);
for (let i of values) {
if (Array.isArray(i)) {
if (i.some(val => !isPrimitive(val)))
return false;
} else {
if (!isPrimitive(i))
return false;
}
}
return true;
};
function isPrimitive(test) {
return typeof test !== 'object'
}
Array and object types all return a 'typeof' 'object'. so you can check against an object instead of checking against multiple conditions.
So the return statement will be:
return (typeof i === 'object').
Number, string, undefined, null will all return false on the statement above.
The attribute(or the nested object) is selected dynamically based on conditions. It can be one of the 4 possibilities as follows:
var tempData = o.title ? o["properties"] || o["items"]["properties"] : o[k]["properties"] || o[k]["items"]["properties"];
Then I get this new data, I want to replace the above selected with.
var newData = //some new Object
I want to replace whatever above selected with the new data. I could do the following (go through the condition again and set the new data):
if(o.title){
if (o["properties"]) {
o["properties"] = newData;
} else if (o["items"]["properties"]) {
o["items"]["properties"] = newData;
}
}else{
if (o[k]["properties"]) {
o[k]["properties"] = newData;
} else if (o[k]["items"]["properties"]) {
o[k]["items"]["properties"] = newData;
}
}
But it doesn't look good. What is the more sophisticated way of achieving this?
It is unclear if you are generically attempting to replace any properties property with the newData, or if you are wanting it to specifically be one of the ones you have specified in your code. I have assumed that you are only wanting to replace the ones you specifically have shown in your code.
Note: The following assumes that it is not possible for the value of the properties property to evaluate to false. If it is possible for it to have a value that evaluates to false, this will fail.
As a first pass, I would do something like:
var p;
if (o.title) {
p=o;
} else {
p=o[k];
}
if (p.properties) {
p.properties = newData;
} else if (p.items.properties) {
p.items.properties = newData;
}
However, that relies on:
o is not null or undefined.
o.title does not evaluate to false, if you are trying to test for the existence of o.title.
k is valid/defined.
p (i.e. o[k]) is not null or undefined (i.e. is an Object)
p.properties does not evaluate to false, if you are testing for existence
p.items is not null or undefined (i.e. is an Object)
p.items.properties does not evaluate to false, if you are testing for existence
A more robust implementation would be:
if (typeof o === 'object' && o !== null) {
var p;
if (o.hasOwnProperty('title')) {
p = o;
} else {
p = o[k];
}
if (typeof p === 'object' && p !== null) {
if (p.hasOwnProperty('properties')) {
p.properties = newData;
} else if (typeof p.items === 'object' && p.items !== null
&& p.items.hasOwnProperty('properties')) {
p.items.properties = newData;
}
}
}
This still relies on:
k is valid/defined.
Basically, it is OK to use shortcuts like if(o.title) to test for existence, if you know that
the possible values for o can not include ones which might make your code throw an error (e.g o is null or undefined), and
the possible values for o.title do not evaluate to false when the property actually exists (e.g. o.title is null, undefined (yes, the property can exist, but have the value undefined), false, 0, '', etc.).
If you are going to perform the replacements in other areas of your code, or if you are going to use property keys other than hard coded items, and properties, then you should create a function. Assuming you are only performing this replacement in this section of your code, using a variable to hold the object in which you are looking for properties is faster/more efficient than creating a function.
Ok, from what i can understand here, it's like you are trying to replace the "properties" with the new data, and you want this to be able to be done dynamically, or maybe i can say, you need to do this regardless the structure.
lets see, if your objective is anything that end up with "properties", lets do it like this:
function recReplace(current,target,replacement){
for (var i in current){
if (i == target){
current[i] = replacement;
}
else{
recReplace(current[i],target,replacement);
}
}
}
And in the end you call
recReplace(o,"properties",newData);
But this will replace whole "properties" key with newData in DFS way, you can do additional conditional if you want to replace it only the first occurence
I am using angular-translate for a big application. Having several people committing code + translations, many times the translation objects are not in sync.
I am building a Grunt plugin to look at both files' structure and compare it (just the keys and overall structure, not values).
The main goals are:
Look into each file, and check if the structure of the whole object
(or file, in this case) is the exact same as the translated ones;
On error, return the key that doesn't match.
It turns out it was a bit more complicated than I anticipated. So i figured I could do something like:
Sort the object;
Check the type of data the value contains (since they are translations, it will only have strings, or objects for the nestings) and store it in another object, making the key equal to the original key and the value would be a string 'String', or an object in case it's an object. That object contains the children elements;
Recursively repeat steps 1-2 until the whole object is mapped and sorted;
Do the same for all the files
Stringify and compare everything.
A tiny example would be the following object:
{
key1: 'cool',
key2: 'cooler',
keyWhatever: {
anotherObject: {
key1: 'better',
keyX: 'awesome'
},
aObject: 'actually, it\'s a string'
},
aKey: 'more awesomeness'
}
would map to:
{
aKey: 'String',
key1: 'String',
key2: 'String',
keyWhatever: {
aObject: 'String',
anotherObject: {
key1: 'String',
keyX: 'String'
}
}
}
After this, I would stringify all the objects and proceed with a strict comparison.
My question is, is there a better way to perform this? Both in terms of simplicity and performance, since there are many translation files and they are fairly big.
I tried to look for libraries that would already do this, but I couldn't find any.
Thank you
EDIT: Thank you Jared for pointing out objects can't be sorted. I am ashamed for saying something like that :D Another solution could be iterating each of the properties on the main translation file, and in case they are strings, compare the key with the other files. In case they are objects, "enter" them, and do the same. Maybe it is even simpler than my first guess. What should be done?
Lets say you have two JSON objects, jsonA and jsonB.
function compareValues(a, b) {
//if a and b aren't the same type, they can't be equal
if (typeof a !== typeof b) {
return false;
}
// Need the truthy guard because
// typeof null === 'object'
if (a && typeof a === 'object') {
var keysA = Object.keys(a).sort(),
keysB = Object.keys(b).sort();
//if a and b are objects with different no of keys, unequal
if (keysA.length !== keysB.length) {
return false;
}
//if keys aren't all the same, unequal
if (!keysA.every(function(k, i) { return k === keysB[i];})) {
return false;
}
//recurse on the values for each key
return keysA.every(function(key) {
//if we made it here, they have identical keys
return compareValues(a[key], b[key]);
});
//for primitives just use a straight up check
} else {
return a === b;
}
}
//true if their structure, values, and keys are identical
var passed = compareValues(jsonA, jsonB);
Note that this can overflow the stack for deeply nested JSON objects. Note also that this will work for JSON but not necessarily regular JS objects as special handling is needed for Date Objects, Regexes, etc.
Actually you do need to sort the keys, as they are not required to be spit out in any particular order. Write a function,
function getComparableForObject(obj) {
var keys = Object.keys(obj);
keys.sort(a, b => a > b ? 1 : -1);
var comparable = keys.map(
key => key + ":" + getValueRepresentation(obj[key])
).join(",");
return "{" + comparable + "}";
}
Where getValueRepresentation is a function that either returns "String" or calls getComparableForObject. If you are worried about circular references, add a Symbol to the outer scope, repr, assign obj[repr] = comparable in the function above, and in getValueRepresentation check every object for a defined obj[repr] and return it instead of processing it recursively.
Sorting an array of the keys from the object works. However, sorting has an average time complexity of O(nâ‹…log(n)). We can do better. A fast general algorithm for ensuring two sets A and B are equivalent is as follows:
for item in B
if item in A
remove item from A
else
sets are not equivalent
sets are equivalent iff A is empty
To address #Katana31, we can detect circular references as we go by maintaining a set of visited objects and ensuring that all descendents of that object are not already in the list:
# poorly written pseudo-code
fn detectCycles(A, found = {})
if A in found
there is a cycle
else
found = clone(found)
add A to found
for child in A
detectCycles(child, found)
Here's a complete implementation (you can find a simplified version that assumes JSON/non-circular input here):
var hasOwn = Object.prototype.hasOwnProperty;
var indexOf = Array.prototype.indexOf;
function isObjectEmpty(obj) {
for (var key in obj) {
return false;
}
return true;
}
function copyKeys(obj) {
var newObj = {};
for (var key in obj) {
newObj[key] = undefined;
}
return newObj;
}
// compares the structure of arbitrary values
function compareObjectStructure(a, b) {
return function innerCompare(a, b, pathA, pathB) {
if (typeof a !== typeof b) {
return false;
}
if (typeof a === 'object') {
// both or neither, but not mismatched
if (Array.isArray(a) !== Array.isArray(b)) {
return false;
}
if (indexOf.call(pathA, a) !== -1 || indexOf.call(pathB, b) !== -1) {
return false;
}
pathA = pathA.slice();
pathA.push(a);
pathB = pathB.slice();
pathB.push(b);
if (Array.isArray(a)) {
// can't compare structure in array if we don't have items in both
if (!a.length || !b.length) {
return true;
}
for (var i = 1; i < a.length; i++) {
if (!innerCompare(a[0], a[i], pathA, pathA)) {
return false;
}
}
for (var i = 0; i < b.length; i++) {
if (!innerCompare(a[0], b[i], pathA, pathB)) {
return false;
}
}
return true;
}
var map = copyKeys(a), keys = Object.keys(b);
for (var i = 0; i < keys.length; i++) {
var key = keys[i];
if (!hasOwn.call(map, key) || !innerCompare(a[key], b[key], pathA,
pathB)) {
return false;
}
delete map[key];
}
// we should've found all the keys in the map
return isObjectEmpty(map);
}
return true;
}(a, b, [], []);
}
Note that this implementation directly compares two objects for structural equivalency, but doesn't reduce the objects to a directly comparable value (like a string). I haven't done any performance testing, but I suspect that it won't add significant value, though it will remove the need to repeatedly ensure objects are non-cyclic. For that reason, you could easily split compareObjectStructure into two functions - one to compare the structure and one to check for cycles.
When I am developing in jQuery, I frequently find myself typing selectors into the Chrome/Firebug console and seeing what they give me. They are always nicely formatted as if they were arrays:
I am trying to work out what it is that makes the console treat an object as an array. For instance, the following custom object is not treated as an array:
function ElementWrapper(id) {
this[0] = document.getElementById(id);
}
If I then add a length property and a splice method, it magically works as an array, with any properties with integer keys treated as members of the arrays:
function ElementWrapper(id) {
this[0] = document.getElementById(id);
this.length = 1;
this.splice = Array.prototype.splice;
}
So essentially my question is: what determines whether the console displays an object as an array? Is there any rationale to it, or is it a completely arbitrary "if an object has these properties, it must be an array?" If so, what are the decisive properties?
This is what Firebug's isArray method does: (from the Firebug source)
if (!obj)
return false;
else if (isIE && !isFunction(obj) && typeof obj == "object" && isFinite(obj.length) && obj.nodeType != 8)
return true;
else if (isFinite(obj.length) && isFunction(obj.splice))
return true;
else if (isFinite(obj.length) && isFunction(obj.callee)) // arguments
return true;
else if (instanceOf(obj, "HTMLCollection"))
return true;
else if (instanceOf(obj, "NodeList"))
return true;
else
return false;
Of course, none of these checks ensures that the object is a true JavaScript array, but they do a reasonable job of guessing whether an object is a pseudo-array, which in turn gives you a convenient array-like representation for debugging.
Chrome may or may not use these same checks, and the new Web Console in Firefox 4 doesn't recognize anything other than true arrays as arrays.