JavaScript初始化和错误处理

Question

I am writing an Angular app, coming from a PHP background. What is the standard approach to initialisation and error handling. For example take my JWT Token factory.

app.factory('Token', ['jwt_decode', function(jwt_decode) {

    var token = null, expiry = null, role = null;

    return {

        get: function() {
            return token;
        },

        set: function(value) {

            token = value;

            var data = jwt_decode(token);

            expiry = data.exp;
            role = data.role;

        },

        clear: function()
        {
            // performed on session expiry or logout.
            token = null;
            expiry = null;
            role = null;
        },

        has: function()
        {
            return token !== null;
        },

        getRole: function()
        {
            return role;
        },

        getExpiry: function()
        {
            return expiry;
        }
    };

}]);

I have initialised my private variables as null but I have read some blogs which instead suggest I leave them as undefined. If I leave them as undefined should my clean method set these back to undefined or null? If I set them to undefined I believe my has function should then be token !== undefined?

Lastly if say a invalid token was passed eg 123 how should this be handled, is it common to throw like I would in PHP? I am yet too see much error handling in JavaScript to know the best way to handle it?

Answer 1

Null or undefined is a matter of style. Choose one of those and be consistent. The key in js test for falsy or thruthy values. That is your has method could return !!token, so if the token is null or undefined or '' will be false and true otherwise. It is a good practice to wrap your code in an self invoking anonymous function and make undefined as a parameter because is not a reserve word in js and anyone could assign a value to undefined.

(function(angular, $, undefined){

}(angular,jQuery));

Exception handling you have try/catch to handle unexpected behavior or you can throw errors (throw 'Unexpected token'). Again you can catch the errors that you throw with try/catch