store a function within the confines of localstorage

Question

store a function within the confines of localstorage

I am currently working with objects that contain data to be displayed and manipulated in a browser. I want to store this data in local storage. To achieve this, I have been using JSON.stringify() to convert the objects into text, which has proven successful.

{
"bindingRef": [],
"primo": {
    "name": "primo",
    "modifiable": true,
    "binded": false,
    "isInteger": false,
    "label": "Numero di Primi"
},
"secondo": {
    "name": "secondo",
    "modifiable": true,
    "binded": false,
    "isInteger": false,
    "label": "Numero di Secondi"
}
}

Now, I am attempting to save a function by converting it to a string before storing it:

JSON.stringify(myFunction.toString());

However, the output looks like this:

"savedFunction": "function () {\n\t\t\t\tvar tot = menu.primo.get() * 6 + menu.secondo.get() * 8 + menu.dolce.get() * 4;\n\t\t\t\tif (menu.sconto.get()) {\n\t\t\t\t\treturn tot * 0.90;\n\t\t\t\t} else {\n\t\t\t\t\treturn tot;\n\t\t\t\t}\n\t\t\t}"

Is this the correct method for saving a function in local storage? Are there alternative approaches that may be more effective? If this is indeed the right way, is there a simple way to remove any tabs or indentation from the string, perhaps through the use of a regular expression?

javascript json local-storage

Answer 1

Answer №1

In JavaScript, functions, like in many other functional languages, act as closures: they contain within them the contents of the environment scope at the time of definition, which includes temporary data such as database or file handles.

However, this can pose problems when it comes to JSON deserialization behavior. Therefore, it is important to carefully assess what is encompassed within the function and what needs to be explicitly defined.

For more insights on this topic, check out this SO thread.

Answer 2

In JavaScript, functions, like in many other functional languages, act as closures: they contain within them the contents of the environment scope at the time of definition, which includes temporary data such as database or file handles.

However, this can pose problems when it comes to JSON deserialization behavior. Therefore, it is important to carefully assess what is encompassed within the function and what needs to be explicitly defined.

For more insights on this topic, check out this SO thread.

Answer 3

Answer №2

If you want to store functions in localStorage, you can encapsulate the function within an object and utilize custom functions like storage.set and storage.get instead of using the standard localStorage.set and localStorage.get (as localStorage does not support adding functions directly, unlike JSON)..

The storage.set function will serialize an object containing functions before using localStorage.setItem().
Similarly, the storage.get function will deserialize an object containing functions after retrieving it with localStorage.getItem().

To enable functions to be stored, I have tailored the JSON.stringify and JSON.parse functions so that they can handle functions as well. This way, you can integrate these modified functions into other parts of your code seamlessly without any name changes. I have simply appended a 2 to the original functions for convenience.

JSON.stringify2 = JSON.stringify;
JSON.parse2 = JSON.parse;

JSON.stringify = function(value) {
    return JSON.stringify2(value, function(key, val) {
        return (typeof val === 'function') ? val.toString().replace(/\t|\n/g, '') : val;
    });
}

JSON.parse = function(value) {
    return JSON.parse2(value, function(key, val) {
        if (typeof val === 'string') {
            var regex = /^function\s*\([^()]*\)\s*{.*}$/;

            if (regex.exec(val) !== null)
                return eval('key = ' + val);
            else
                return val;
        } else
            return val;
    });
}

var storage = {};

storage.set = function(key, value) {
    if (typeof value === 'object')
        value = JSON.stringify(value);

    localStorage.setItem(key, value);
}

storage.get = function(key) {
    var value = localStorage.getItem(key);

    try {
        return JSON.parse(value);
    } catch (e) {
        return value;
    }
}

Answer 4

If you want to store functions in localStorage, you can encapsulate the function within an object and utilize custom functions like storage.set and storage.get instead of using the standard localStorage.set and localStorage.get (as localStorage does not support adding functions directly, unlike JSON)..

The storage.set function will serialize an object containing functions before using localStorage.setItem().
Similarly, the storage.get function will deserialize an object containing functions after retrieving it with localStorage.getItem().

To enable functions to be stored, I have tailored the JSON.stringify and JSON.parse functions so that they can handle functions as well. This way, you can integrate these modified functions into other parts of your code seamlessly without any name changes. I have simply appended a 2 to the original functions for convenience.

JSON.stringify2 = JSON.stringify;
JSON.parse2 = JSON.parse;

JSON.stringify = function(value) {
    return JSON.stringify2(value, function(key, val) {
        return (typeof val === 'function') ? val.toString().replace(/\t|\n/g, '') : val;
    });
}

JSON.parse = function(value) {
    return JSON.parse2(value, function(key, val) {
        if (typeof val === 'string') {
            var regex = /^function\s*\([^()]*\)\s*{.*}$/;

            if (regex.exec(val) !== null)
                return eval('key = ' + val);
            else
                return val;
        } else
            return val;
    });
}

var storage = {};

storage.set = function(key, value) {
    if (typeof value === 'object')
        value = JSON.stringify(value);

    localStorage.setItem(key, value);
}

storage.get = function(key) {
    var value = localStorage.getItem(key);

    try {
        return JSON.parse(value);
    } catch (e) {
        return value;
    }
}

store a function within the confines of localstorage

Answer №1

Answer №2

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