function - Javascript: use either a variable, or if it's undefined, a default string

Question

I have this code:

var phrase = function (variable, defaultPhrase) {
    if (typeof variable === "undefined") {
        return defaultPhrase;
    }
    else {
        return variable;
    }
}

It's called like this:

Ext.Msg.show({title: phrase(js_shutdown,'Shutdown'), //...

What I want to do is to use a default phrase when the variable is not defined, but when I pass an undefined variable to phrase(), JS throws an undefined variable error. How do I fix this? Any other ideas to do this?

Answer 1

You don't need a function. The || operator is usually used:

Ext.Msg.show({ title: js_shutdown || 'Shutdown', //...

You can see || as:

someValue || defaultValue

For strings, defaultValue is used if someValue === "".

If the variable is not defined at all, you'll need to inline the typeof x === "undefined" check, because you cannot pass the variable to a function (that's a ReferenceError).