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It is often derided as being a toy, but beneath its layer of deceptive simplicity, powerful language features await.
And Array , which is a special kind of object. And Date and RegExp , which are objects that you get for free.
And to be technically accurate, functions are just a special type of object. So the type diagram looks more like this:. And there are some built-in Error types as well. Things are a lot easier if we stick with the first diagram, however, so we'll discuss the types listed there for now.
This can be important for bit-wise operations. The standard arithmetic operators are supported, including addition, subtraction, modulus or remainder arithmetic, and so forth. There's also a built-in object that we forgot to mention earlier called Math that provides advanced mathematical functions and constants:.
You can convert a string to an integer using the built-in parseInt function. This takes the base for the conversion as an optional second argument, which you should always provide:. In older browsers, strings beginning with a "0" are assumed to be in octal radix 8 , but this hasn't been the case since or so.
Unless you're certain of your string format, you can get surprising results on those older browsers:. Here, we see the parseInt function treat the first string as octal due to the leading 0, and the second string as hexadecimal due to the leading "0x".
For this reason, we sometimes speak simply of "true values" and "false values," meaning values that become true and false , respectively, when converted to booleans.
So if a variable is defined using var in a compound statement for example inside an if control structure , it will be visible to the entire function. However, starting with ECMAScript , let and const declarations allow you to create block-scoped variables. These can be used as a prefix or postfix operators.