Develop Reference

JS-Interpreter - changing “this” context

JS-Interpreter is a somewhat well-known JavaScript Interpreter. It has security advantages in that it can completely isolate your code from document and allows you to detect attacks such as infinite loops and memory bombs. This allows you to run externally defined code safely.
I have an object, say o like this:
let o = {
hidden: null,
regex: null,
process: [
"this.hidden = !this.visible;",
"this.regex = new RegExp(this.validate, 'i');"
],
visible: true,
validate: "^[a-z]+$"
};
I'd like to be able to run the code in process through JS-Interpreter:
for (let i = 0; i < o.process.length; i++)
interpretWithinContext(o, o.process[i]);
Where interpretWithinContext will create an interpreter using the first argument as the context, i.e. o becomes this, and the second argument is the line of code to run. After running the above code, I would expect o to be:
{
hidden: false,
regex: /^[a-z]+$/i,
process: [
"this.hidden = !this.visible;",
"this.regex = new RegExp(this.validate, 'i');"
],
visible: true,
validate: '^[a-z]+$'
}
That is, hidden and regex are now set.
Does anyone know if this is possible in JS-Interpreter?

I’ve spent a while messing around with the JS-Interpreter now, trying to figure out from the source how to place an object into the interpreter’s scope that can be both read and modified.
Unfortunately, the way this library is built, all the useful internal things are minified so we cannot really utilize the internal things and just put an object inside. Attempts to add a proxy object also failed failed since the object just wasn’t used in a “normal” way.
So my original approach to this was to just fall back to providing simple utility functions to access the outside object. This is fully supported by the library and probably the safest way of interacting with it. It does require you to change the process code though, in order to use those functions. But as a benefit, it does provide a very clean interface to communicate with “the outside world”. You can find the solution for this in the following hidden snippet:
function createInterpreter (dataObj) {
function initialize (intp, scope) {
intp.setProperty(scope, 'get', intp.createNativeFunction(function (prop) {
return intp.nativeToPseudo(dataObj[prop]);
}), intp.READONLY_DESCRIPTOR);
intp.setProperty(scope, 'set', intp.createNativeFunction(function (prop, value) {
dataObj[prop] = intp.pseudoToNative(value);
}), intp.READONLY_DESCRIPTOR);
}
return function (code) {
const interpreter = new Interpreter(code, initialize);
interpreter.run();
return interpreter.value;
};
}
let o = {
hidden: null,
regex: null,
process: [
"set('hidden', !get('visible'));",
"set('regex', new RegExp(get('validate'), 'i'));"
],
visible: true,
validate: "^[a-z]+$"
};
const interprete = createInterpreter(o);
for (const process of o.process) {
interprete(process);
}
console.log(o.hidden); // false
console.log(o.regex); // /^[a-z]+$/i
<script src="https://neil.fraser.name/software/JS-Interpreter/acorn_interpreter.js"></script>
However, after posting above solution, I just couldn’t stop thinking about this, so I dug deeper. As I learned, the methods getProperty and setProperty are not just used to set up the initial sandbox scope, but also as the code is being interpreted. So we can use this to create a proxy-like behavior for our object.
My solution here is based on code I found in an issue comment about doing this by modifying the Interpreter type. Unfortunately, the code is written in CoffeeScript and also based on some older versions, so we cannot use it exactly as it is. There’s also still the problem of the internals being minified, which we’ll get to in a moment.
The overall idea is to introduce a “connected object” into the scope which we will handle as a special case inside the getProperty and setProperty to map to our actual object.
But for that, we need to overwrite those two methods which is a problem because they are minified and received different internal names. Fortunately, the end of the source contains the following:
// Preserve top-level API functions from being pruned/renamed by JS compilers.
// …
Interpreter.prototype['getProperty'] = Interpreter.prototype.getProperty;
Interpreter.prototype['setProperty'] = Interpreter.prototype.setProperty;
So even if a minifier mangles the names on the right, it won’t touch the ones on the left. So that’s how the author made particular functions available for public use. But we want to overwrite them, so we cannot just overwrite the friendly names, we also need to replace the minified copies! But since we have a way to access the functions, we can also search for any other copy of them with a mangled name.
So that’s what I’m doing in my solution at the beginning in patchInterpreter: Define the new methods we’ll overwrite the existing ones with. Then, look for all the names (mangled or not) that refer to those functions, and replace them all with the new definition.
In the end, after patching the Interpreter, we just need to add a connected object into the scope. We cannot use the name this since that’s already used, but we can just choose something else, for example o:
function patchInterpreter (Interpreter) {
const originalGetProperty = Interpreter.prototype.getProperty;
const originalSetProperty = Interpreter.prototype.setProperty;
function newGetProperty(obj, name) {
if (obj == null || !obj._connected) {
return originalGetProperty.call(this, obj, name);
}
const value = obj._connected[name];
if (typeof value === 'object') {
// if the value is an object itself, create another connected object
return this.createConnectedObject(value);
}
return value;
}
function newSetProperty(obj, name, value, opt_descriptor) {
if (obj == null || !obj._connected) {
return originalSetProperty.call(this, obj, name, value, opt_descriptor);
}
obj._connected[name] = this.pseudoToNative(value);
}
let getKeys = [];
let setKeys = [];
for (const key of Object.keys(Interpreter.prototype)) {
if (Interpreter.prototype[key] === originalGetProperty) {
getKeys.push(key);
}
if (Interpreter.prototype[key] === originalSetProperty) {
setKeys.push(key);
}
}
for (const key of getKeys) {
Interpreter.prototype[key] = newGetProperty;
}
for (const key of setKeys) {
Interpreter.prototype[key] = newSetProperty;
}
Interpreter.prototype.createConnectedObject = function (obj) {
const connectedObject = this.createObject(this.OBJECT);
connectedObject._connected = obj;
return connectedObject;
};
}
patchInterpreter(Interpreter);
// actual application code
function createInterpreter (dataObj) {
function initialize (intp, scope) {
// add a connected object for `dataObj`
intp.setProperty(scope, 'o', intp.createConnectedObject(dataObj), intp.READONLY_DESCRIPTOR);
}
return function (code) {
const interpreter = new Interpreter(code, initialize);
interpreter.run();
return interpreter.value;
};
}
let o = {
hidden: null,
regex: null,
process: [
"o.hidden = !o.visible;",
"o.regex = new RegExp(o.validate, 'i');"
],
visible: true,
validate: "^[a-z]+$"
};
const interprete = createInterpreter(o);
for (const process of o.process) {
interprete(process);
}
console.log(o.hidden); // false
console.log(o.regex); // /^[a-z]+$/i
<script src="https://neil.fraser.name/software/JS-Interpreter/acorn_interpreter.js"></script>
And that’s it! Note that while that new implementation does already work with nested objects, it may not work with every type. So you should probably be careful what kind of objects you pass into the sandbox. It’s probably a good idea to create separate and explicitly safe objects with only basic or primitive types.

Have not tried JS-Interpreter. You can use new Function() and Function.prototype.call() to achieve requirement
let o = {
hidden: null,
regex: null,
process: [
"this.hidden = !this.visible;",
"this.regex = new RegExp(this.validate, 'i');"
],
visible: true,
validate: "^[a-z]+$"
};
for (let i = 0; i < o.process.length; i++)
console.log(new Function(`return ${o.process[i]}`).call(o));

Hi may be interpretWithinContext look like something like that ?
let interpretWithinContext = (function(o, p){
//in dunno for what you use p because all is on object o
o.hidden = (o.hidden === null) ? false : o.hidden;
o.regex = (o.regex === null) ? '/^[a-z]+$/i' : o.regex;
console.log(o);
return o;
});
https://codepen.io/anon/pen/oGwyra?editors=1111

Angular deep compare objects except for specific properties

Use case:
$scope.$watch('settings', function (newVal, oldVal) {
if (!angular.equals(oldVal, newVal)) {
setDirty();
}
}, true);
Now this is practically the same as
$scope.$watch('settings', function (newVal, oldVal) {
if (oldVal) {
setDirty();
}
}, true);
Since the $watch already compares the two.
However, there is one property that even though it changes i don't want to setDirty().
This is my working (hacky) solution so far:
$scope.$watch('settings', function (newVal, oldVal) {
if (!oldVal) return;
var editedOldVal = angular.copy(oldVal, {});
var editedNewVal = angular.copy(newVal, {});
delete editedOldVal.propertyIDontWannaWatch;
delete editedNewVal.propertyIDontWannaWatch;
if (!angular.equals(editedOldVal, editedNewVal)) {
setDirty();
}
}, true);
Is there a cleaner way to make angular.equals() or the $watch ignore specific properties?
EDIT:
This answer does not solve my problem since option 1 is not a solution at all, says that if the property that i don't want to watch hasn't changed - do nothing, but this is exactly the property i want to ignore (don't care if it changed or not). option 2 makes that property not comparable at all, i only want to ignore it on this specific case and not make it uncomparable by definition.

You can prefix properties with a $ and it will not be included in the equals comparison. The angular.equals method ignores properties that start with a $.
From the Angular.js code:
if (key.charAt(0) === '$' || isFunction(o1[key])) continue;
For example:
var object1 = {propertyOne: '1', $myCustomHiddenField: 'something'};
var object2 = {propertyOne: '1', $myCustomHiddenField: 'something else'};
var result = angular.equals(object1, object2);//this is true
The equals method can be referenced here.

Ember - Custom Computed Property to check if all dependent fields exists

I am creating a form and I am trying to find a simple, elegant way of handling to see if all inputs exist.
Form = Ember.Object.extend({
// section 1
name: null,
age: null,
isABoolean: null,
// section 2
job: null,
numberOfSiblings: null,
isComplete: Ember.computed.and('_isSection1Complete', '_isSection2Complete'),
_isSection1Complete: function() {
var isPresent = Ember.isPresent;
return isPresent(this.get('name')) && isPresent(this.get('age')) && isPresent(this.get('isABoolean'));
}.property('name', 'age', 'isABoolean'),
_isSection2Complete: function() {
var isPresent = Ember.isPresent;
return isPresent(this.get('job')) && isPresent(this.get('numberOfSiblings'));
}.property('job', 'numberOfSiblings')
});
However, this doesn't seem to scale. My actual application will have many sections (over 20 sections).
I am looking into trying to create a re-usable computed property that fits my needs. Take for example the code of what I am going for:
Form = Ember.Object.extend({
// properties...
isComplete: Ember.computed.and('_isSection1Complete', '_isSection2Complete'),
_isSection1Complete: Ember.computed.allPresent('name', 'age', 'isABoolean'),
_isSection2Complete: Ember.computed.allPresent('job', 'numberOfSiblings')
});
I feel that this is a common case, but I'm failing to find the correct computed properties on how to execute this, so I would like to make my own.
Two questions:
Where's the best place to define the custom computed property? Can I just attach a function to Ember.computed?
Is there an easier way to solve this? I feel like I'm overlooking something simple.

As for Question #1,
You can define a custom computed helper in the App namespace. In this example, I created a new computed helper called allPresent that checks each property passed in against Ember.isPresent.
App.computed = {
allPresent: function (propertyNames) {
// copy the array
var computedArgs = propertyNames.slice(0);
computedArgs.push(function () {
return propertyNames.map(function (propertyName) {
// get the value for each property name
return this.get(propertyName);
}, this).every(Ember.isPresent);
});
return Ember.computed.apply(Ember.computed, computedArgs);
}
};
It can be used like this, per your example code:
_isSection2Complete: App.computed.allPresent(['job', 'numberOfSiblings'])
I adapted this from the approach here: http://robots.thoughtbot.com/custom-ember-computed-properties
As for Question #2, I can't think of a simpler solution.

I had to make a minor adjustment to Evan's solution, but this works perfectly for anyone else that needs it:
App.computed = {
allPresent: function () {
var propertyNames = Array.prototype.slice.call(arguments, 0);
var computedArgs = propertyNames.slice(0); // copy the array
computedArgs.push(function () {
return propertyNames.map(function (propertyName) {
// get the value for each property name
return this.get(propertyName);
}, this).every(Ember.isPresent);
});
return Ember.computed.apply(Ember.computed, computedArgs);
}
};
This can now be used as such:
_isSection2Complete: App.computed.allPresent('job', 'numberOfSiblings')

How can I make Ember.js handlebars #each iterate over objects?

I'm trying to make the {{#each}} helper to iterate over an object, like in vanilla handlebars. Unfortunately if I use #each on an object, Ember.js version gives me this error:
Assertion failed: The value that #each loops over must be an Array. You passed [object Object]
I wrote this helper in attempt to remedy this:
Ember.Handlebars.helper('every', function (context, options) {
var oArray = [];
for (var k in context) {
oArray.push({
key : k,
value : context[k]
})
}
return Ember.Handlebars.helpers.each(oArray, options);
});
Now, when I attempt to use {{#every}}, I get the following error:
Assertion failed: registerBoundHelper-generated helpers do not support use with Handlebars blocks.
This seems like a basic feature, and I know I'm probably missing something obvious. Can anyone help?
Edit:
Here's a fiddle: http://jsfiddle.net/CbV8X/

Use {{each-in}} helper. You can use it like like {{each}} helper.
Example:
{{#each-in modelWhichIsObject as |key value|}}
`{{key}}`:`{{value}}`
{{/each-in}}
JS Bin demo.

After fiddling with it for a few hours, I came up with this hacky way:
Ember.Handlebars.registerHelper('every', function(context, options) {
var oArray = [], actualData = this.get(context);
for (var k in actualData) {
oArray.push({
key: k,
value: actualData[k]
})
}
this.set(context, oArray);
return Ember.Handlebars.helpers.each.apply(this,
Array.prototype.slice.call(arguments));
});
I don't know what repercussions this.set has, but this seems to work!
Here's a fiddle: http://jsfiddle.net/CbV8X/1/

I've been after similar functionality, and since we're sharing our hacky ways, here's my fiddle for the impatient: http://jsfiddle.net/L6axcob8/1/
This fiddle is based on the one provided by #lxe, with updates by #Kingpin2k, and then myself.
Ember: 1.9.1, Handlebars: 2.0.0, jQuery 2.1.3
Here we are adding a helper called every which can iterate over objects and arrays.
For example this model:
model: function() {
return {
properties: {
foo: 'bar',
zoo: 'zar'
}
};
}
can be iterated with the following handlebars template:
<ul class="properties">
{{#every p in properties}}
<li>{{p.key}} : {{p.value}}</li>
{{/every}}
</ul>
every helper works by creating an array from the objects keys, and then coordinating changes to Ember by way of an ArrayController. Yeah, hacky. This does however, let us add/remove properties to/from an object provided that object supports observation of the [] property.
In my use case I have an Ember.Object derived class which notifies [] when properties are added/removed. I'd recommend looking at Ember.Set for this functionality, although I see that Set been recently deprecated. As this is slightly out of this questions scope I'll leave it as an exercise for the reader. Here's a tip: setUnknownProperty
To be notified of property changes we wrap non-object values in what I've called a DataValueObserver which sets up (currently one way) bindings. These bindings provide a bridge between the values held by our internal ArrayController and the object we are observing.
When dealing with objects; we wrap those in ObjectProxy's so that we can introduce a 'key' member without the need to modify the object itself. Why yes, this does imply that you could use #every recursively. Another exercise for the reader ;-)
I'd recommend having your model be based around Ember.Object to be consistent with the rest of Ember, allowing you to manipulate your model via its get & set handlers. Alternatively, as demonstrated in the fiddle, you can use Em.Get/Em.set to access models, as long as you are consistent in doing so. If you touch your model directly (no get/set), then every won't be notified of your change.
Em.set(model.properties, 'foo', 'asdfsdf');
For completeness here's my every helper:
var DataValueObserver = Ember.Object.extend({
init: function() {
this._super();
// one way binding (for now)
Em.addObserver(this.parent, this.key, this, 'valueChanged');
},
value: function() {
return Em.get(this.parent, this.key);
}.property(),
valueChanged: function() {
this.notifyPropertyChange('value');
}
});
Handlebars.registerHelper("every", function() {
var args = [].slice.call(arguments);
var options = args.pop();
var context = (options.contexts && options.contexts[0]) || this;
Ember.assert("Must be in the form #every foo in bar ", 3 == args.length && args[1] === "in");
options.hash.keyword = args[0];
var property = args[2];
// if we're dealing with an array we can just forward onto the collection helper directly
var p = this.get(property);
if (Ember.Array.detect(p)) {
options.hash.dataSource = p;
return Ember.Handlebars.helpers.collection.call(this, Ember.Handlebars.EachView, options);
}
// create an array that we will manage with content
var array = Em.ArrayController.create();
options.hash.dataSource = array;
Ember.Handlebars.helpers.collection.call(this, Ember.Handlebars.EachView, options);
//
var update_array = function(result) {
if (!result) {
array.clear();
return;
}
// check for proxy object
var result = (result.isProxy && result.content) ? result.content : result;
var items = result;
var keys = Ember.keys(items).sort();
// iterate through sorted array, inserting & removing any mismatches
var i = 0;
for ( ; i < keys.length; ++i) {
var key = keys[i];
var value = items[key];
while (true) {
var old_obj = array.objectAt(i);
if (old_obj) {
Ember.assert("Assume that all objects in our array have a key", undefined !== old_obj.key);
var c = key.localeCompare(old_obj.key);
if (0 === c) break; // already exists
if (c < 0) {
array.removeAt(i); // remove as no longer exists
continue;
}
}
// insert
if (typeof value === 'object') {
// wrap object so we can give it a key
value = Ember.ObjectProxy.create({
content: value,
isProxy: true,
key: key
});
array.insertAt(i, value);
} else {
// wrap raw value so we can give it a key and observe when it changes
value = DataValueObserver.create({
parent: result,
key: key,
});
array.insertAt(i, value);
}
break;
}
}
// remove any trailing items
while (array.objectAt(i)) array.removeAt(i);
};
var should_display = function() {
return true;
};
// use bind helper to call update_array if the contents of property changes
var child_properties = ["[]"];
var preserve_context = true;
return Ember.Handlebars.bind.call(context, property, options, preserve_context, should_display, update_array, child_properties);
});
Inspired by:
How can I make Ember.js handlebars #each iterate over objects?
http://mozmonkey.com/2014/03/ember-getting-the-index-in-each-loops/
https://github.com/emberjs/ember.js/issues/4365
https://gist.github.com/strathmeyer/1371586
Here's that fiddle again if you missed it:
http://jsfiddle.net/L6axcob8/1/

Dojo widget variable reference still held after doh test

I've been creating some tests for my Dojo widget to check that boolean flags are being set correctly. However, I've found that since I have altered my constructor to pass in an object, previously ran tests seem to affect the subsequent tests.
I've tried destroying the widget in the tear down methods, but whatever I seem to do, the value persists.
Can anyone suggest what I might be doing wrong?
My widget code:
var showControls = true;
return declare([WidgetBase, TemplatedMixin, _WidgetsInTemplateMixin], {
templateString: template,
constructor: function (params) {
this.showControls = (typeof params.showControls === "undefined" || typeof params.showControls != "boolean") ? this.showControls : params.showControls;
}
});
My test class is:
var customWidget;
doh.register("Test controls", [
{
name: "Test controls are not visible when set in constructor",
runTest: function() {
var params = { showControls: false };
customWidget = new CustomWidget(params);
doh.assertFalse(customWidget.getShowControls());
}
},
{
name: "Test controls are visible when set in constructor with string instead of boolean",
runTest: function() {
var params = { showControls: "wrong" };
customWidget= new CustomWidget(params);
doh.assertTrue(customWidget.getShowControls());
}
}
]);
So, the first test passes, as showControls is set to false, however the 2nd test attempts to create a new instance, in which the constructor will check that the value is a boolean. When I debug this however, it thinks showControls starts out as 'false', not true.
Any clues?!
Thanks

dijit/_WidgetBase has a mechanism of mixing in constructor parameters and it is the reason of the behavior you described. One of the possible solutions is to define a custom setter as a method _set[PropertyName]Attr:
var defaults = {
showControls: true
}
var CustomWidget = declare([_WidgetBase, _TemplatedMixin], {
templateString: "<div></div>",
constructor: function(params) {
declare.safeMixin(this, defaults);
},
_setShowControlsAttr: function(value) {
this.showControls = (typeof value === "boolean") ? value : defaults.showControls;
}
});
See it in action: http://jsfiddle.net/phusick/wrBHp/

I would suggest you list any members of your widget, if you do not, things passed into the constructor may not be properly recognised. It seems you want to use this.showControls, so you should have a showControls member. like this :
return declare([WidgetBase, TemplatedMixin, _WidgetsInTemplateMixin], {
templateString: template,
showControls: true, // default value
constructor: function (params) {
// no further action, params are automatically mixed in already
}
});
Be careful when listing members, dojo interprets arrays and objects as class members (like static in Java, AFAIK they're attached to the prototype) so if you want each object to have e.g., a separate array of values, list it as null and initialize in your constructor.