Localstorage and array-CodePudding

  public arraySuccess = [];

  ngOnInit(): void {
    this.arraySuccess = JSON.parse(localStorage.getItem('success'));
  }
  openDialog(String) {
    this.dialog.open(RecommendationsDialog);

    if(this.arraySuccess != null && 
       this.arraySuccess.includes(String)) {
      return
    } else if (this.arraySuccess != null) {
      this.arraySuccess.push(String);
    }

    localStorage.setItem('success', JSON.stringify(this.arraySuccess));
    console.log(this.arraySuccess);

  }

There are articles (3 pcs). When opening, I would like to add their name to the localstorage. And if the user visits the page again, the read checkbox would be ticked. (checking if the given name is in the localstorage array)

But the problem is that I get null in the console.

Where did I make a mistake?

CodePudding user response：

Null value handling

Since localStorage.getItem() returns a value or null, you might want to ensure that arraySuccess is an array before calling the push method :

this.arraySuccess = JSON.parse(localStorage.getItem('success')) ?? [];

This way, even if it returns null, you'll save your element.

Also, declare your variable like so (instead of String) :

openDialog(myString: string) {
    this.dialog.open(RecommendationsDialog);
    if(this.arraySuccess.includes(myString)) {
      return
    } else {
      this.arraySuccess.push(myString);
    }
    localStorage.setItem('success', JSON.stringify(this.arraySuccess));
  }

Cheers

Edit: modified null handling thanks to Heretic Monkey