反应.js。 当我尝试使用 FileReader 上传超过 3 个图像文件时，仅上传了 3 个

Question

the next function is getting file and setting it in state obj (arr: [readerEvent.target.result]). works fine when uploading one file, fine with 2 and 3.

when I am trying to upload more then 3 files - only 3 uploaded . I can see that the full (5) list of files is coming into the func by using console.log.

input:
    <Input
      onChange={handleChange}
      type="file"
      // accept="image/png, image/jpeg"
      multiple
    />
----------------------------------------
Component:
    const list = Object.keys(e.target.files).map((elm) => e.target.files[elm]);

    list.map((file, index) => {
          loadFile(file, index, setImagesList);
    });

---------------------------------------------------------------------------------------
Util:
export default function loadFile(file, index, setImagesList) {
  //   console.log("another file ", file);
  let image = new Image();
  var reader = new FileReader();
  reader.onloadend = function (readerEvent) {
    image.src = readerEvent.target.result;
    image.onload = function () {
      setImagesList((old) => [
        ...old,
        {
          key: `${Date.now()}-${file.name}-${index}`,
          arr: [readerEvent.target.result],
          imageOriginalWidth: image.width,
          imageOriginalHeight: image.height,
        },
      ]);
    };
  };
  reader.onerror = function (event) {
    console.error("File could not be read! Code " + event.target.error.code);
  };
  reader.readAsDataURL(file);
}

Answer 1

OK found a solution so I will share it. sending to the util function the entire list and handle it there. in util func I will update a state that will be the optional loaded file . only after a check I will set the "real" images list - that will happen out of the util - inside the component:

 useEffect(()=>{
   uploaded.map((obj, index) => {
      if (isValid) {
        setImagesList((old) => [...old, obj]);
      }
},[uploaded])
-----------------------------------
util :
export default function loadFiles(files, setUploaded) {
  const reader = new FileReader();
  let arr = [];
  function readFile(index) {
    if (index >= files.length || index > 5) {
      setUploaded(arr);
      return;
    }
    const file = files[index];
    reader.onload = function (e) {
      let image = new Image();
      image.src = e.target.result;
      image.onload = function () {
        arr.push({
          key: `${Date.now()}-${file.name}-${index}`,
          name: file.name,
          arr: [e.target.result],
          imageOriginalWidth: image?.width,
          imageOriginalHeight: image?.height,
        });
        readFile(index + 1);
      };
    };
    reader.readAsDataURL(file);
  }
  readFile(0);
}

good luck!