如何在JavaScript中调用方法onload

Question

So I want to call a function Local.getThis onload with this code:

    class Local {
        getThis() {
            let that;
            if (localStorage.getItem('that') === null) {
                that = [];
                console.log(that);
                localStorage.setItem('that', that);
            } else {
                that=JSON.parse(localStorage.getItem('that'));
                console.log(that);
            }
        }

    // DOM Load Event 
    document.addEventListener('DOMContentLoaded', Local.getThis)

But nothing is happening, no error nothing. But when I change "getThis" to STATIC it works (Output: []). Does it need to be STATIC ??

PS

After setting that = []; I get an error

'Uncaught SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at HTMLDocument.getThis'

on the next reload but that is probably a whole other problem I guess.

EDIT:

For the record the error was related to localStorage.setItem('that', that); , it should be ofcourse localStorage.setItem('that', JSON.stringify(that));

Answer 1

part 1: this is a reserved word in JavaScript, change parameter's name.

part 2: Local is a class, so to access a function directly from it that function must be static. Otherwise an instance needs to be initiated first. and the function can then be used from that instance.

Answer 2

You should create an instance of Local class first to have this

const local = new Local();
document.addEventListener('DOMContentLoaded', local.getThis.bind(local))
//or
document.addEventListener('DOMContentLoaded', function() {
  local.getThis();
})

Update

Also you cannot use variable name this as it is reserved word. If you don't need a context ( this ) you can create a method as a static method:

class Local{}
Local.getThis = function() {
 // code without this
}

so then you can use as you've written:

document.addEventListener('DOMContentLoaded', local.getThis);

Answer 3

But nothing is happening, no error nothing. But when I change "getThis" to STATIC it works (Output: []). Does it need to be STATIC ??

To call your method as Local.getThis need to be static .

Otherwise you need to create an instance of Local.

var local = new Local();
document.addEventListener('DOMContentLoaded', function() {
  local.getThis();
})