How to declare string constants in JavaScript? [duplicate]

Answer 1

Many browsers' implementations (and Node) have constants, used with const.

const SOME_VALUE = "Your string";

This const means that you can't reassign it to any other value.

Check the compatibility notes to see if your targeted browsers are supported.

Alternatively, you could also modify the first example, using defineProperty() or its friends and make the writable property false. This will mean the variable's contents can not be changed, like a constant.

Answer 2

Just declare variable outside of scope of any js function. Such variables will be global.

Answer 3

Use global namespace or global object like Constants.

var Constants = {};

And using defineObject write function which will add all properties to that object and assign value to it.

function createConstant (prop, value) {
    Object.defineProperty(Constants , prop, {
      value: value,
      writable: false
   });
};

Answer 4

Of course, this wasn't an option when the OP submitted the question, but ECMAScript 6 now also allows for constants by way of the "const" keyword:

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/const

You can see ECMAScript 6 adoption here.

Answer 5

There's no constants in JavaScript, but to declare a literal all you have to do is:

var myString = "Hello World";

I'm not sure what you mean by store them in a resource file; that's not a JavaScript concept.

Answer 6

So many ways to skin this cat. You can do this in a closure. This code will give you a read-only , namespaced way to have constants. Just declare them in the Public area.

//Namespaced Constants
var MyAppName;
//MyAppName Namespace
(function (MyAppName) {
    //MyAppName.Constants Namespace
    (function (Constants) {
        //Private
        function createConstant(name, val) {
            Object.defineProperty(MyAppName.Constants, name, {
                value: val,
                writable: false
            });
        }

        //Public
        Constants.FOO = createConstant("FOO", 1);
        Constants.FOO2 = createConstant("FOO2", 1);

        MyAppName.Constants = Constants;
    })(MyAppName.Constants || (MyAppName.Constants = {}));
})(MyAppName || (MyAppName = {}));

Usage:

console.log(MyAppName.Constants.FOO);       //prints 1
MyAppName.Constants.FOO = 2;
console.log(MyAppName.Constants.FOO);       //does not change - still prints 1