Is It Safe To Download Javascript UPD

Type safety is a complex topic and there's no one agreed definition of what exactly a "type-safe" language is. But by almost any definition of it, no, JavaScript is not type-safe. :-) In that particular example, though, JavaScript did provide runtime type safety: It didn't actually try to call i and cause some kind of memory access exception or similar; instead, when your code tried to call it, the first thing the JavaScript engine did was check to see if it was callable and, since it isn't, it raised a protective error.

But a type-safe language tries to discourage or prevent errors or undesireable behavior due to using an incorrect type, through type enforcement (both at the compilation/parsing stage and when the code runs). JavaScript mostly doesn't do that (the above notwithstanding); in general, JavaScript tends to coerce instead.

Is It Safe To Download Javascript

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Type-safe languages also typically (though I don't think always) have typed variables/parameters/properties and similar and do at least some type checking at compilation/parsing stage rather than when the relevant code runs. In those languages, i would have had a type associated with it (e.g., int i rather than var i), and the code trying to call it as a function would have failed at the compilation/parsing stage, rather than later when it was run as it does in JavaScript. JavaScript, on the other hand, doesn't have typed variables/parameters/properties at all. A variable can hold an object one moment and a primitive number the next.

In language with static type safety (e.g., compilation/parsing stage type safety), there'd be type information associated with the str argument and the error would be when the code was compiled/parsed.

In contrast C ist not type safe (although it checks code at compile time) because you can create cases where it will not throw an exception, but just do something random. (see pages 3 and 4 of the Why Rust book for an example)The implicit type coercions which are present in Javascript (e.g. casting the number 1 to a string 1 for string concatenation: 1 + '2') is a well defined operation.

Note that being type safe is mostly independent of whether a language checks types at compile time or at run time: C checks at compile time, and is not type safe; Python checks at runtime, and is type safe. Any practical type-safe language must do at least some checks (array bounds checks, for example) at runtime.

I have tried to google but don't seem to find any answer. What is the use of "safe" here? And when do we use it? If you have any reference or articles I could refer to, that would be extremely helpful. Thank you so much!

This is an idiomatic pattern in JavaScript, but it gets verbose when the chain is long, and it's not safe. For example, if obj.first is a Falsy value that's not null or undefined, such as 0, it would still short-circuit and make nestedProp become 0, which may not be desirable.

How do I make sure that the libraries I use are safe? Couldn't someone bad use a library to steal things from my webpage/data? Are there any best-practices I could use to prevent this or is there some way to check if a library is safe? How do you guys deal with this in the 'real' world?

While encoding adds an extra character before a potentially dangerous character, such as the \ character before the quotation mark in JavaScript, escaping converts a character into an equivalent but safe format, for instance the > character into the > string in HTML.

Following these JavaScript security best practices can help you make your scripts safer and prevent common attacks, such as cross-site scripting, cross-site request forgery, third-party security vulnerabilities, and others.

It is not. Or more exactly it is as safe as the browser implementation is. Browsers (including their JavaScript engine) are complex pieces of software, with regular addition of new features - because users want them.

The blog describe the discovery of a 0day that allows arbitrary code execution in WebKit and how that's used to exploit another 0day in the macOS Window Manager to escape the sanbox Safari is running in (that's a macOS sandbox, not a Safari's one) to escalate to "root" and own the system.

Long story short, by simply visiting a link while having JavaScript enabled, a macOS system can be totally compromised without a single glitch visible to the user.

That's how safe JavaScript can be: As safe as a complex piece of software as WebKit's JSCore can be.

That's why users that require high security are advised to disable JavaScript (that's a fairly common requirement in the DarkWeb, for example).

But as a rule JavaScript has never been safe within the browser. Malicious code developers are constantly finding ways to exploit how each engine works as well as its available JavaScript functionality to achieve malicious goals.

In the first few years, JavaScript was rather dangerous within the browser. Now it is a constant race between malicious code developers and the browser/engine developers and eventually the malicious developers always win, even if just for a short time. So JavaScript can hardly be called safe. "Should be safe for now" is a more accurate way to put it.

It is which is why many users consider it unsafe and block it using browser extensions. JavaScript allows websites to track users in ways not possible without it including identifying users after they have deleted their cookies by fingerprinting the browser. Many of the newer web APIs like WebUSB allow things that are not at all safe but browsers will request user permission when accessing unsafe APIs like USB and camera.

Today, the great majority of code executing in the browser is written in JavaScript. With the rise of WebAssembly, we will likely see the browser platform switch from the primarily single language lock in of today (like a mainframe of the past) to an open platform where any WebAssembly compliant language can be used. This will, in a way, prove that JavaScript isn't particularly safe/special, as at that point many languages will be executing in the browser. All of these languages will use the sandbox provided by the browser to execute.

JavaScript is "relatively safe," but not "absolutely safe." Any code you run on your system has a potential to do harm. There is no perfectly safe system, except for the one that never used. JavaScript is safer than putting an unknown USB device in your computer, and safer than a binary you download from a shady website or get in a suspect email attachment, and much safer than some of the scripts you'll find on websites that tell you to copy-paste them in to your shell.

It has safety features: a sandbox to help isolate the process, a relatively limited API that has security constraints to help avoid running arbitrary computer instructions, and security controls meant to limit exposure of sensitive data like fingerprints or cross-domain data sharing. These are on top of your operating system's controls applied to the browser binary to limit bad behavior, and anti-virus applications that can help stop such attacks.

However, it is not absolutely safe. Bugs in the browser's runtime engine, the browser itself, the anti-virus, or even the processor itself can all compromise JavaScript's security. The system is only as secure as its weakest security. The security of JavaScript is mostly meant to prevent "casual" exploits (such as an 8-year-old learning JavaScript for the first time and accidentally writing an exploit), but doesn't stand a chance against dedicated attackers. JavaScript is complicated enough that there are bound to be bugs, perhaps in weird and unexpected ways.

Generally speaking, any typical script you might run in to on a typical website is probably "safe", especially those linked to by major search engines. However, once you start going off the beaten path, it is incredibly likely you'll get your system compromised at some point if there's even a single weak point. It only takes one really good exploit, or sometimes two or three in tandem, to completely take over a system.

As it is, only enable JavaScript for sites you trust (I personally use NoScript for this purpose), always keep all your software up to date, and always pay attention to browser warnings like invalid certificates and so on. Even then, you won't be 100% safe, but you'll be taking an active part in your own mitigation strategy.

It's safe because it was designed to be safe. Or at least it's safe to the point where a less than formal "JavaScript is pretty powerful" does suggest the it's probably sufficiently safe to reassure you. In practice, no piece of software is perfectly safe, so it's a matter of degree. Javascript is safe enough that most corporations are willing to let employees visit websites using company hardware.

But in general, it is "safe" to execute such scripts because lots of security experts have spent a lot of time making sure that feeling of safety is justified. But it all depends on your threat model. If you had billions of dollars on the line, you might not even want to trust JavaScript's safety!

So the real question is what is your bar for "safe?" Do you consider Windows to be safe? What about Internet Explorer? Adobe Acrobat Reader? OpenJPEG? The Linux kernel? OpenSSL? Safety and usability are always at odds. You have to use something (or maybe you don't. The Amish haven't been hit with a 0-day yet... unless you count a new strain of Influenza) To really understand if you can call something "safe" or not you need a threat model, defining how someone might attack you, and a usability model defining what usability you need to achieve while mitigating the threat model. Without those, we have to read into your words and your history to guess what "safe" means. 2351a5e196