Javascript Cookbook¶
Functions¶
Functions in Javascript have really changed over the past ten years or so.
Function Declarations¶
Defining functions using declarations used to the the usual way of using functions. Declared functions are not executed immediately. They are executed later - when they are invoked.
Example¶
function myfunction(a, b) {
return a * b;
}
myfunction(2, 3);
Anonymous Functions¶
You can define a function without a name. Such functions are known as anonymous functions.
Example¶
You can pass an anonymnous function as a parameter in another function call.
setTimeout(function() {
alert('hello');
}, 1000);
Function Expressions¶
You can also define an anonymous function using an expression, and you can store a function exression in a variable. You invoke the function by stating the variable name followed by a set of parenthesis and a semicolon.
Example¶
var sayhi = function() {
alert('Hello World!');
}
sayhi();
But what problem do function expressions solve? Why were they added to the Javasctipt language?
Closures¶
When you wrap an anonymous function definition in a set of parenthesis, you can invoke it by appending a set of parenthesis to it, followed by a semicolon.
Example¶
(function() {
alert('foo');
})();
Lambdas¶
Lambdas provide a shorthand for creating anyonymous functions.
