JSON 中的意外令牌 a 在 position 0 在 JSON.parse

Question

About

I am trying to save items in LocalStorage by:

document.querySelector('form').addEventListener('submit', function(e){
    e.preventDefault();
    let input = document.getElementById('task').value;
    let tasks;
    if(localStorage.getItem('tasks') === null) {
        tasks = [];
    } else {
        tasks = JSON.parse(localStorage.getItem('tasks'));
    }
    tasks.push(input);
    localStorage.setItem('tasks', JSON.stringify(tasks))
})

Issue

This doesn't seem to be saving my values, and I get the error:

Unexpected token a in JSON at position 0 at JSON.parse

Any help is appreciated!

Answer 1

Try clearing your localStorage and running your code again. If you had a previous value saved in there that was not a valid JSON-parsable object, it would never be over-ridden since your code would fail before that.

If that does not work, try replacing localStorage with window.localStorage .

Answer 2

What I would do is the following:

var myjson = localStorage.getItem('tasks');
console.log(myjson);
if (myjson === null ) {
    tasks = [];
} else{
    tasks = JSON.parse(myjson);
}

Confirm myjson is a valid json object.

You can use jsonlint to validate your json object.

Answer 3

This might a problem in setting the local storage as well. Please make sure that the value that you are trying to set in the local storage is being saved.

If the above is true then you can proceed with something like the below code:

var objJson = localStorage.getItem('tasks');

objTasks = objJson ? JSON.parse(objJson) : [];

The above lines of code is going to make sure that the value for the local storage "tasks" is retrieved and if its retrieved and the value isn't null and not empty then and then only it will get parsed.