How to save functions in localStorage API HTML5 [duplicate]

Question

I am trying to save an array in localStorage but it contains functions (called promise) in an object of the array, but the problem appears when I convert array to string using JSON.stringify, apparently all functions are removed and when I parse string to JSON Object it comes without methods.

/* Example code */

var storage = {
	getListUsers: function(){
		return {
			name: 'name',
			age: 'age'
		}
	},
	active: true,
	data: []
}

var convert = JSON.stringify(storage);
localStorage.setItem('data', convert);

Best regards.

Answer 1

Few observations :

• Functions don't exist in JSON. Look into the official document json.org.
• A value can be a string in double quotes, or a number, or true or false or null, or an object or an array but not a method.
• Why method inside an JSON Object ? Methods is basically used to manipulate the data. You can work with data outside of the JSON object as well.

You can use JSON.stringify replacer function to convert the function into string while converting to JSON string.

DEMO

var storage = {
	getListUsers: function() {
		return {
			name: 'name',
			age: 'age'
		}
	},
	active: true,
	data: []
}

var json = JSON.stringify(storage, function(key, value) {
  if (typeof value === 'function') {
    return value.toString();
  } else {
    return value;
  }
});

console.log(json);

Answer 2

You can set the JavaScript which should be set at localStorage as .textContent of a <script> element, get the .textContent of the element to set at localStorage. You can then set the same text at a different <script> element or convert the text to a data URI which can be posted to other browsing contexts or a server.

<script id="storage">
/* Example code */

var storage = {
  getListUsers: function() {
    return {
      name: 'name',
      age: 'age'
    }
  },
  active: true,
  data: []
}
</script>
<script>
var convert = document.getElementById("storage");

localStorage.setItem("data", convert.textContent);

console.log(localStorage.getItem("data"));    
</script>