使用承诺从 localStorage async 检索时出错

Question

I am getting an error when trying to get data from localStorage.

Have attached my code below, and included comments to what I think should be happening with each step. I have also swapped the JSON data to a sample data set.

async function getData() {
    var dataAll = localStorage.getItem('requestAll')
    // check if data is in cache
    if( dataAll === null ) {
       // if it is not in cache then request it
       var responseAll = await fetch('https://data.cityofchicago.org/resource/xzkq-xp2w.json')
  
       // parse the json response
       dataAll = await responseAll.json()
       
       // store the data in the cache
       localStorage.setItem('requestAll', JSON.stringify(dataAll));
    } else {
       // if it exists then parse it
       dataAll = JSON.parse(dataAll)
    }
  
    // return the data
    return dataAll
  }
  
  function waitForDomReady() {
  return new Promise(resolve => $(resolve))
  }

  
  async function run() {
  try {
  
      var dataAll = await getData();        
      await waitForDomReady();
      console.log(dataAll);    
  
  
      var jsonString = localStorage.getItem("requestAll");
      var dataAll = JSON.parse(jsonString);
          
      
      
     
  
  } catch (err) {
      console.log('error occured')
  }
  }
  
  
  run(); 

  
  async function grabNewData() {
  var dataAll = localStorage.getItem('requestAll')
     // fetch new data from json source
    var responseAll = await fetch('https://data.cityofchicago.org/resource/xzkq-xp2w.json')
  
     // parse the json response
     dataAll = await responseAll.json()
     
     // store the new data in the cache ready for use
     localStorage.setItem('request', JSON.stringify(dataAll));
     
     console.log('New data stored');
  
  // return the new data
  return dataAll
  }
  
  setTimeout(function(){
       grabNewData()
        console.log('Checking for new records');
  }, 10);
  

EDIT: As per below, I have discovered that the code worked fine. The source was too big.

Thank you.

Answer 1

I made a codesandbox of your code refactored.

Code on Codesandbox

The code looks like this:

Note: The code won't run properly on Stackoverflow, since you are making a request and using localstorage.

 function getData() { console.log("running"); // check fir requestAll in local storage. null if it doesn't exist. const cache = localStorage.getItem("requestAll"); // if the data is in the cache, return it. if (cache) return Promise.resolve(JSON.parse(cache)); // else get the data and store it. return Promise.resolve( fetch("https://data.cityofchicago.org/resource/xzkq-xp2w.json") .then((res) => res.json()) .then((data) => { localStorage.setItem("requestAll", JSON.stringify(data)); return data; }) ); } (() => { getData().then(console.log); })();

Answer 2

Script worked fine. The JSON data source was too big to store in cache.