JavaScript has the types Object, Array, Boolean, Number, String, and Function. Types and Constructors Constructing Built-in Types with the 'new' Keyword But if you're doing that, you're probably after Number.MAX_VALUE or Number.MIN_VALUE. It does make sense really, since Math.max() is returning the largest of an empty list of numbers. Looking at a with block in isolation, it isn't possible to tell exactly what is happening. John Resig finds a number of clever uses for it in his book, but also concedes that it has a performance hit and can be a little confusing. The with statement gives you a shorthand for accessing the properties of an object, and there are conflicting views on whether it should be used. Use an actual function as that parameter.įinally, the Function constructor is much the same as eval - the only difference being that it will be executed in the global context. The setTimeout and setInterval functions can take a string as its first parameter which will be interpreted, so that shouldn't be done either. Even better, you can use the jQuery.parseJSON function which will always work. There is also the JSON.stringify function for the opposite use. Parsing JSON is a common usage normally people will use " var obj = eval(jsonText) ", however almost all browsers now support the native JSON object which you can use instead: " var obj = JSON.parse(jsonText) ".
TYPEOF JAVASCRIPT CODE
Additionally, the code being eval'd is executed in the current scope, so it can modify local variables and add stuff to your scope which may be unintended.
![typeof javascript typeof javascript](https://cd.linuxscrew.com/wp-content/uploads/2021/08/javascript-typeof-feature.jpg)
It looks quite ugly, too, because in most cases it is misused. It's slow - when JavaScript is loaded into the browser, it gets compiled into native code however, every time an eval statement is reached during execution, the compilation engine has to be started up all over again, and that is quite expensive. evalĮval interprets a string as code but its use is generally frowned upon.
![typeof javascript typeof javascript](https://miro.medium.com/max/1400/1*_lPLRJJJHoS7gTg50FZ0cg.png)
The same goes for NodeList objects returned by DOM calls such as getElementsByTagName - they can also be converted to proper arrays using the above code. For example:Ĭopy Code var args = (arguments, 0) This means that you can compare objects of two different types and it will attempt to convert them to the same type before performing a comparison. The = operator performs a comparison with type coercion.
![typeof javascript typeof javascript](https://i.ytimg.com/vi/JXdvbHuKfdI/maxresdefault.jpg)
TYPEOF JAVASCRIPT SOFTWARE
This article is an introduction to the weird side of JavaScript, and it definitely has a weird side! Software developers who usually write code in another language will find a lot of intriguing "features" when they begin to write code in the world's most widely used language.