Writing and Reading 'persistent' data using FlashEEPROM (journaling) module

Try this exercise:

//Uint8Trick.js
//30 Aug 2016
var i;

console.log("Create an object with an Uint8Array");
var A={B:512,C:new Uint8Array(16)};
for(i=0;i<16;i++)A.C[i]=i;
console.log("A= ",A);

console.log("Stringify the object");
var D=JSON.stringify(A);
console.log("D= ",D);

console.log("Parse it back returns undefined");
var F=JSON.parse(D);
console.log("F= ",F); //F is undefined

//notice I skipped E to avoid conflict with E.toUint8Array

//the trick
console.log("apply btoa trick");
A.C=btoa(A.C);
console.log("A= ",A);

console.log("stringify");
var D=JSON.stringify(A);
console.log("D= ",D);

console.log("parse");
var F=JSON.parse(D);
console.log("F= ",F);

//the trick in reverse
console.log("reverse the trick");
F.C=E.toUint8Array(atob(F.C));
console.log("Frev= ",F);

and the output

>echo(0);
Create an object with an Uint8Array
A=  { "B": 512,
  "C": new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
 }
Stringify the object
D=  {"B":512,"C":new Uint8Array([0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15])}
Parse it back returns undefined
F=  undefined
apply btoa trick
A=  { "B": 512,
  "C": "AAECAwQFBgcICQoLDA0ODw=="
 }
stringify
D=  {"B":512,"C":"AAECAwQFBgcICQoLDA0ODw=="}
parse
F=  { "B": 512,
  "C": "AAECAwQFBgcICQoLDA0ODw=="
 }
reverse the trick
Frev=  { "B": 512,
  "C": new Uint8Array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15])
 }
=undefined

1 Attachment

• Uint8Trick.js