Question 273285 in Reactjs Question posted in
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Reactjs – how to solve error possibly 'null' for typescript

hey guys i try to make handlesave and handle clik like below but i am new to typescript and get error for cropRef.current

error:

‘cropRef.current’ is possibly ‘null’.

here the code handle save

 const handleSave = async () => {
    if (cropRef) {
      const dataUrl = cropRef.current.getImage().toDataURL();
      const result = await fetch(dataUrl);
      const blob = await result.blob();
      setPreview(URL.createObjectURL(blob));
      setModalOpen(false);
    }
  };

error:

‘inputRef.current’ is possibly ‘null’.

code handle click

const handleInputClick = (e) => {
    e.preventDefault();
    inputRef.current.click();
  };

do you guys know how to solve this kind of error ? please tell me in detail because i am still learning about typescript its new to me

Tags:

2

Answers


  1. 0

    cropRef and inputRef is not defined anywhere in your code. I am assuming possibly indicates that the compiler cant tell what the attachment is because the value has not been defined (typescript specific). In JavaScript, I think the error would be can not read value of undefined.

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  2. 0

    When you use the useRef hook in React, for example to get a handle on an HTML element that you can render, it’s common practice to give the ref a default value of null.

    This default value will be the ref’s value until it’s set to something else. For example, if it’s being set to an HTML element via a ref prop then it will remain null during the component’s initial render pass, when it hasn’t yet been inserted into the DOM, (and it would also be null if the ref is on an element that isn’t always rendered).

    import React, { useEffect, useRef } from 'react';

function MyComponent() {
    const rootRef = useRef<HTMLDivElement>(null);

    console.log(rootRef.current); // <- `null` the first time, then a `HTMLDivElement`

    useEffect(() => {
        console.log(rootRef.current); // <- Always a `HTMLDivElement`, because `useEffect` runs after rendering
    }, [])

    return <div ref={rootRef}></div>;
}

    TypeScript Playground

    If you use createRef and you don’t pass a default value, null will be used by default as well. It’s not clear from your question exactly how your ref is created.

    The easiest way to deal with this is just to check that cropRef.current !== null, so you’ll never try to access properties on it while it is null. Depending on what possible values might be stored in your ref, sometimes just a check for truthiness might be enough, i.e. if (cropRef.current) { // ...

    Sometimes, you may find it convenient to just use optional chaining to access a property via ?. only if your ref’s current value is not null or undefined, e.g. cropRef.current?.getImage().toDataURL()

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