Default arguments/parameters in JavaScript

When designing your functions, it’s often helpful to be able to assign default values for arguments/parameters that aren’t passed later. Unlike programming languages like PHP, JavaScript doesn’t provide this functionality inherently. Undefined arguments are, well: undefined.

var sayHello = function (name) {
    console.log('Hello, ' + name);
}

By using the shortcut computation of boolean expressions, you can define a default value for each argument which is assigned if the argument is originally undefined.

var sayHello = function (name) {
    name = name || 'Nobody';
    console.log('Hello, ' + name);
}

While sayHello('Peter') still works, sayHello() (called without any arguments) would now result Hello, Nobody. Neat.

JavaScriptJavaScript