How should I proceed when encountering a TypeScript error stating "Object may be null"?

Within the compilerOptions section of my tsconfig.json configuration file, I have enabled the strictNullChecks setting to true.

Every now and then, when utilizing functions such as getElementById("...") or querySelector("..."), a non-fatal warning pops up:

TS2531: Object is possibly 'null'

While I understand the reason behind this warning (occasionally, the element is not yet loaded or cannot be located), what is the best course of action to take in response to this error?

Would it suffice to wrap the code that interacts with the element(s) inside an if condition, similar to the following example:

let divs: HTMLElement | null = document.getElementById("div");
if(divs !== null) {
  // carry out operations with divs...
}

Alternatively, should I implement a different approach?

Your advice is greatly appreciated.

typescripterror-handlingnullcompiler-options

Answer №1

Is it appropriate to include the code that utilizes certain elements within an if condition?

Absolutely. In cases where the element may not exist, checking for its presence is definitely recommended.

If you find yourself frequently using getElementById or querySelector with full confidence that the element will always be present, consider creating a helper function that throws an error instead of returning null:

function getGuaranteed(id: string): HTMLElement {
    const el = document.getElementById(id);
    if (el == null) {
        throw new Error("Element #" + id + " not found.");
    }
    return el as HTMLElement;
}

Utilize this function in situations where you are certain that the element will be available.

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