generate a download file in javascript

如何透過 javascript 產生下載檔案的功能

how to download text files via javascript

  var textToSave = 'this is a test';
  var hiddenElement = document.createElement('a');
  hiddenElement.href = 'data:attachment/text,' + encodeURIComponent(textToSave);
  hiddenElement.target = '_blank';
  hiddenElement.download = 'myFile.txt';
  hiddenElement.click();

上面的範例，如果是使用 encodeURI 很容易遇到內容跳脫的問題，例如：內容有# 就掛了，檔案內容很容易被中斷，建議使用 encodeURIComponent 。

這2者的差別：

>>> encodeURI("bla&bla&bla")
"bla&bla&bla"

>>> encodeURIComponent("bla&bla&bla")
"bla%26bla%26bla"

>>> encodeURI('[{"id":1,"href":"#"}]')
%5B%7B%22id%22:1,%22href%22:%22#%22%7D%5D

>>> encodeURIComponent('[{"id":1,"href":"#"}]')
%5B%7B%22id%22%3A1%2C%22href%22%3A%22%23%22%7D%5D

差異在 # encodeURI 時還是 #, encodeURIComponent 變成 %3A

下載 svg 圖片的範例：

  const svgBlob = new Blob([svgData], {
    type: "image/svg+xml;charset=utf-8",
  });
  const objectUrl = URL.createObjectURL(svgBlob);
  const downloadLink = document.createElement("a");
  downloadLink.href = objectUrl;
  downloadLink.download = filename;
  document.body.appendChild(downloadLink);
  downloadLink.click();
  document.body.removeChild(downloadLink);