|Language:||English, Spanish, Portuguese|
|Distribution:||Free* [*Sign up for free]|
In strict mode, referencing a a this value of null or undefined throws an error. Disallows duplicate parameter values. Strict mode throws an error when it detects a duplicate named argument for a function e.
Makes eval safer. There are some differences in the way eval behaves in strict mode and in non-strict mode. Most significantly, in strict mode, variables and functions declared inside of an eval statement are not created in the containing scope they are created in the containing scope in non-strict mode, which can also be a common source of problems.
Throws error on invalid usage of delete. The delete operator used to remove properties from objects cannot be used on non-configurable properties of the object. Non-strict code will fail silently when an attempt is made to delete a non-configurable property, whereas strict mode will throw an error in such a case. Consider the two functions below.
Will they both return the same thing?
How can you reliably test if a value is equal to NaN? This special value results from an operation that could not be performed either because one of the operands was non-numeric e.
While this seems straightforward enough, there are a couple of somewhat surprising characteristics of NaN that can result in hair-pulling bugs if one is not aware of them. A better solution would either be to use value! Also, ES6 offers a new Number.
Design of button is UI, but interaction with button is UX. How to test website performance. Website performance play a major role. As per Think With Google website, a website is excellent id its loading time is under 5 seconds. A website is fair if loading time is 5 to 8 seconds. But a website is poor if loading time is more than 8 seconds.
Which one do you use typically? Does HTML needs compiler? Whereas Asp. They need a compiler or interpreter which can convert their code in machine language.
HTML5 introduced semantic tags like header, nav,article,section, aside, footer and figcaption. These tags convey the containing content. It may seem harmless, but if you do this all over the place, you will soon find yourself in a big mess that you cannot get out of. Nothing else can override it, apart from another!
And so the cycle continues. How do margin, border and padding fit together in the box model? While the border is pretty self-explanatory, it can be somewhat confusing to see the difference between margin and padding.
The easiest way to understand is to look at a visual representation of it. Looking at the below image, the very centre rectangle is the size of your element. Immediately surrounding that is padding. Then comes the border, and only then comes the margin. This means that if your element has a background color, that color will also fill the padding.
Margin adds empty space around your element. That means that the aforementioned background color will not fill the margin. Interested in web development? Enter your email address Fonts Something that has almost always come up for me is the way you size your text, mainly focused on the units you use. Defining your font sizes in em allows you to change the size of your text based on the size defined at a higher level.
For example, if a container has specified a font-size of 2em, and you specify a font-size of 2em on an element inside that container, that element has an effective font-size of 4em! However, this can be a little confusing as you might not always see the size you expect!
It scales well in the browser, just like em and px, but it uses a base size.
From that, all further rem values are calculated. For example, if your base rem value is equal to 16px, then 1rem will always be equal to 16px, 2rem will always be equal to 32px, and so on.
What are web safe fonts and fallback fonts? Not all operating systems and browsers have the same fonts installed. Web safe fonts are fonts that are commonly pre-installed on many computer systems, such as Arial and Times New Roman. Ubuntu , you should choose a web safe fallback font to display e.
Arial , followed by a generic font family e. Media queries How would you use media queries in a mobile-first approach? The most common approach is the mobile-first one. All styles outside of media queries are targeted at mobile devices. Then, through progressively larger media queries, you can style larger screens one step at a time. How do you handle browser differences in your user base?