my_function.__name__ Using __name__ is the preferred method as it applies uniformly. Unlike func_name, it works on built-in functions as well: >>> import time >>> time.time.func_name Traceback (most recent call last): File “<stdin>”, line 1, in ? AttributeError: ‘builtin_function_or_method’ object has no attribute ‘func_name’ >>> time.time.__name__ ‘time’ Also the double underscores indicate to the reader this … Read more
There are two typical ways of declaring a function. I prefer the second approach. function function_name { command… } or function_name () { command… } To call a function with arguments: function_name “$arg1” “$arg2” The function refers to passed arguments by their position (not by name), that is $1, $2, and so forth. $0 is … Read more
JavaScript syntax 101: here is a function declaration: function foo() {} Note that there’s no semicolon; this is just a function declaration. You would need an invocation, foo(), to actually run the function. Now, when we add the seemingly innocuous exclamation mark: !function foo() {} it turns it into an expression. It is now a … Read more
TLDR JavaScript has lexical (also called static) scoping and closures. This means you can tell the scope of an identifier by looking at the source code. The four scopes are: Global – visible by everything Function – visible within a function (and its sub-functions and blocks) Block – visible within a block (and its sub-blocks) … Read more
You want the typeof operator. Specifically: if (typeof variable !== ‘undefined’) { // the variable is defined }
From ES6/ES2015, default parameters are in the language specification. function read_file(file, delete_after = false) { // Code } just works. Reference: Default Parameters – MDN Default function parameters allow formal parameters to be initialized with default values if no value or undefined is passed. In ES6, you can simulate default named parameters via destructuring: // … Read more
The difference is that apply lets you invoke the function with arguments as an array; call requires the parameters be listed explicitly. A useful mnemonic is “A for array and C for comma.” See MDN’s documentation on apply and call. Pseudo syntax: theFunction.apply(valueForThis, arrayOfArgs) theFunction.call(valueForThis, arg1, arg2, …) There is also, as of ES6, the … Read more