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var x1 = 0; // A global variable, because it is not in any function let x2 = 0; // Also global, this time because it is not in any block function f {var z = 'foxes', r = 'birds'; // 2 local variables m = 'fish'; // global, because it wasn't declared anywhere before function child {var r = 'monkeys'; // This variable is local and does not affect the "birds" r of the parent function. z ...
Modern JavaScript handles associative arrays, using the Map and WeakMap classes. A map does not contain any keys by default; it only contains what is explicitly put into it. The keys and values can be any type (including functions, objects, or any primitive).
JavaScript (/ ˈ dʒ ɑː v ə s k r ɪ p t /), often abbreviated as JS, is a programming language and core technology of the Web, alongside HTML and CSS. 99% of websites use JavaScript on the client side for webpage behavior. [10] Web browsers have a dedicated JavaScript engine that executes the client code.
Integers consisting of two or more digits are written, as a string, by concatenating 1-digit arrays with the plus operator. For example, the string "10" can be expressed in JavaScript as [1] + [0] .
Previously, JavaScript only supported function scoping using the keyword var, but ECMAScript 2015 added the keywords let and const, allowing JavaScript to support both block scoping and function scoping. JavaScript supports automatic semicolon insertion, meaning that semicolons that normally terminate a statement in C may be omitted in ...
Douglas Crockford originally wrote json2.js as an API for reading and writing his (then up-and-coming) JSON data format. It became so widely used that browser vendors decided to implement its API natively and turn it into a de facto standard ; Since json2.js now implements features native to newer browsers into older browsers, it has become a ...
Many languages have explicit pointers or references. Reference types differ from these in that the entities they refer to are always accessed via references; for example, whereas in C++ it's possible to have either a std:: string and a std:: string *, where the former is a mutable string and the latter is an explicit pointer to a mutable string (unless it's a null pointer), in Java it is only ...
contains(string,substring) returns boolean Description Returns whether string contains substring as a substring. This is equivalent to using Find and then detecting that it does not result in the failure condition listed in the third column of the Find section. However, some languages have a simpler way of expressing this test. Related