ecmascript-5

Situation: I found something strange concerning strict mode in Javascript. I am using an external, third-party Javascript library which was minified, has over 4000 lines of code, is not using use strict at all, and is using arguments.callee . I am using use strict in my own code, scoped within a function. When I call one of the functions provided by the library, it throws an error. However, the error is thrown only if I am using use strict the error is thrown in all browsers except Chrome Code: I've removed all the unrelated stuff and reduced the code into this ( online demo on jsFiddle ): //

I'm wondering when I should use Object.defineProperty to create new properties for an object. I'm aware that I'm able to set things like enumerable: false but when do you need this really? If you just set a property like myObject.myprop = 5; its descriptors are all set to true, right? I'm actually more curious when you guys use that rather verbose call to .defineProperty() and for what reasons. Object.defineProperty is mainly used to set properties with specific property descriptors (e.g. read-only (constants), enumerability (to not show a property in a for (.. in ..) loop, getters, setters).

So, I'm looking at the ES5 specification at the definition of what new Object and Object do. To my surprise: new Object describes a whole algorithm of how the object constructor works - treating what happens with different kinds of values. Basically calls ToObject on non objects - identity on objects and builds on null and undefined. Object has a special first step for null and undefined where it builds an object and then calls ToObject on primitives and identity on objects. After reading the description a few times - they seem identical. However, clearly from the spec they do something

Is there anyway to check if strict mode 'use strict' is enforced , and we want to execute different code for strict mode and other code for non-strict mode. Looking for function like isStrictMode();//boolean The fact that this inside a function called in the global context will not point to the global object can be used to detect strict mode: var isStrict = (function() { return !this; })(); Demo: > echo '"use strict"; var isStrict = (function() { return !this; })(); console.log(isStrict);' | node true > echo 'var isStrict = (function() { return !this; })(); console.log(isStrict);' | node false

Bounty Edit: I'm looking for code written in a pure prototypical OO paradigm (think Self). Not a mixture of prototypical OO and classical OO. I don't want to see generic OO wrappers but simply usage of prototypical OO techniques and only prototypical OO techniques. Reference Related Question: Prototypical OO in JavaScript In the above question I mainly focused on Can write prototypical OO like this? Do we need constructors and initialization logic, What are the alternatives? New question: Basically are there any good examples of javascript prototypical OO in large open source projects?

Here are a few examples. // case 1: var obj1 = {msg : 'Hello'}; var obj2 = obj1; obj2.msg = "Hi!"; //overwrites alert(obj1.msg); //=>'Hi!' // case 2: var obj1 = {msg : 'Hello'}; var obj2 = Object.create(obj1); obj2.msg = "Hi!"; //does not overwrite alert(obj1.msg); //=>'Hello' // case 3: var obj1 = {data: { msg : 'Hello'}} var obj2 = Object.create(obj1); obj2.data.msg = "Hi!"; //overwrites, Why? alert(obj1.data.msg); //=>'Hi!' I think Object.create() just gives both makes both point to the same prototype, while assignment makes both object point to same location(not just prototype). But then

I have a set over which I am iterating in ES6. I am trying to convert it to its equivalent in ES5. My build is getting failed because of ES6. That's why I am converting it to ES5. Here's my code in ES6 service.getDevices = function (date) { var result = []; var deviceList = devices[date.getTime()]; for (let item of deviceList) { // browser compatibility: support for ECMA6 result.push({"deviceName": item}); } return result; } I am getting error because of 'let'. I tried using for (var item in deviceList) , it does not display the charts. I also tried this: for(var i = 0; i < deviceList.length()