Typescript error resolution when using json.parse with localstorage.getitem

In the use of similar

JSON.parse(localStorage.getItem(xxxx))
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An error is reported when using “, as shown in the figure below:

Reason: The first argument to json. parse must be of type string

But localstorage. getItem can return a string or null

Solutions:

• Use typeof to check whether the type returned by localStorage.getItem is string

  let LOGIN_DATA;
  let _LOGIN_DATA_KEY = localStorage.getItem(xxxx);
  if (typeof _LOGIN_DATA_KEY === "string") {
    LOGIN_DATA = JSON.parse(_LOGIN_DATA_KEY);
  }
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• Add compatibility to json.parse

  JSON.parse(localStorage.getItem(xxxx) || '{}');
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• Add type assertion (not recommended) : If localstorage.getitem (XXXX) is indeed a null, an error is reported at runtime

  const LOGIN_DATA = JSON.parse( localStorage.getItem(xxxx) as string );
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