JavaScript-Methode zum Schreiben von Dateien auf lokal

Manchmal müssen Sie Dateien bei der Arbeit lokal über JavaScript speichern. Wir alle wissen, dass JavaScript aus Sicherheitsgründen nicht direkt auf lokale Dateien zugreifen darf. IE kann ein VB-Plug-in verwenden, aber weder Chrome noch Firefox unterstützen JavaScript zum lokalen Schreiben von Dateien, daher gibt es Kompatibilitätsprobleme mit dem VB-Plug-in.

Gibt es eine geeignete Methode? Die Antwort lautet: Ja, wir können unsere Anforderungen durch das kleine Plug-in FileSaver.js erfüllen. Schauen wir uns einen bestimmten Codeabschnitt an:

/**
 * 下载文件
 */
var downloadTextFile = function(mobileCode) {
  if(isEmpty(mobileCode)) {
    mobileCode = '';
  }
  var file = new File([mobileCode], "手机号.txt", { type: "text/plain;charset=utf-8" });
  saveAs(file);
}

In diesem Beispiel wird eine Textdatei mit dem Namen „Mobiltelefonnummer.txt“ lokal unter Verwendung des Zeichenkodierungsformats gespeichert auf „UTF-8“, wodurch das Problem verstümmelter chinesischer Zeichen vermieden wird. Wenn Sie schlau sind, probieren Sie es jetzt aus!

Im Anhang finden Sie den vollständigen Quellcode der FileSaver.js-Datei:

/* FileSaver.js
 * A saveAs() FileSaver implementation.
 * 1.3.2
 * 2016-06-16 18:25:19
 *
 * By Eli Grey, http://eligrey.com
 * License: MIT
 *  See https://github.com/eligrey/FileSaver.js/blob/master/LICENSE.md
 */
/*global self */
/*jslint bitwise: true, indent: 4, laxbreak: true, laxcomma: true, smarttabs: true, plusplus: true */
/*! @source http://purl.eligrey.com/github/FileSaver.js/blob/master/FileSaver.js */
var saveAs = saveAs || (function(view) {
  "use strict";
  // IE <10 is explicitly unsupported
  if (typeof view === "undefined" || typeof navigator !== "undefined" && /MSIE [1-9]\./.test(navigator.userAgent)) {
    return;
  }
  var
     doc = view.document
     // only get URL when necessary in case Blob.js hasn&#39;t overridden it yet
    , get_URL = function() {
      return view.URL || view.webkitURL || view;
    }
    , save_link = doc.createElementNS("http://www.w3.org/1999/xhtml", "a")
    , can_use_save_link = "download" in save_link
    , click = function(node) {
      var event = new MouseEvent("click");
      node.dispatchEvent(event);
    }
    , is_safari = /constructor/i.test(view.HTMLElement) || view.safari
    , is_chrome_ios =/CriOS\/[\d]+/.test(navigator.userAgent)
    , throw_outside = function(ex) {
      (view.setImmediate || view.setTimeout)(function() {
        throw ex;
      }, 0);
    }
    , force_saveable_type = "application/octet-stream"
    // the Blob API is fundamentally broken as there is no "downloadfinished" event to subscribe to
    , arbitrary_revoke_timeout = 1000 * 40 // in ms
    , revoke = function(file) {
      var revoker = function() {
        if (typeof file === "string") { // file is an object URL
          get_URL().revokeObjectURL(file);
        } else { // file is a File
          file.remove();
        }
      };
      setTimeout(revoker, arbitrary_revoke_timeout);
    }
    , dispatch = function(filesaver, event_types, event) {
      event_types = [].concat(event_types);
      var i = event_types.length;
      while (i--) {
        var listener = filesaver["on" + event_types[i]];
        if (typeof listener === "function") {
          try {
            listener.call(filesaver, event || filesaver);
          } catch (ex) {
            throw_outside(ex);
          }
        }
      }
    }
    , auto_bom = function(blob) {
      // prepend BOM for UTF-8 XML and text/* types (including HTML)
      // note: your browser will automatically convert UTF-16 U+FEFF to EF BB BF
      if (/^\s*(?:text\/\S*|application\/xml|\S*\/\S*\+xml)\s*;.*charset\s*=\s*utf-8/i.test(blob.type)) {
        return new Blob([String.fromCharCode(0xFEFF), blob], {type: blob.type});
      }
      return blob;
    }
    , FileSaver = function(blob, name, no_auto_bom) {
      if (!no_auto_bom) {
        blob = auto_bom(blob);
      }
      // First try a.download, then web filesystem, then object URLs
      var
         filesaver = this
        , type = blob.type
        , force = type === force_saveable_type
        , object_url
        , dispatch_all = function() {
          dispatch(filesaver, "writestart progress write writeend".split(" "));
        }
        // on any filesys errors revert to saving with object URLs
        , fs_error = function() {
          if ((is_chrome_ios || (force && is_safari)) && view.FileReader) {
            // Safari doesn&#39;t allow downloading of blob urls
            var reader = new FileReader();
            reader.onloadend = function() {
              var url = is_chrome_ios ? reader.result : reader.result.replace(/^data:[^;]*;/, &#39;data:attachment/file;&#39;);
              var popup = view.open(url, &#39;_blank&#39;);
              if(!popup) view.location.href = url;
              url=undefined; // release reference before dispatching
              filesaver.readyState = filesaver.DONE;
              dispatch_all();
            };
            reader.readAsDataURL(blob);
            filesaver.readyState = filesaver.INIT;
            return;
          }
          // don&#39;t create more object URLs than needed
          if (!object_url) {
            object_url = get_URL().createObjectURL(blob);
          }
          if (force) {
            view.location.href = object_url;
          } else {
            var opened = view.open(object_url, "_blank");
            if (!opened) {
              // Apple does not allow window.open, see https://developer.apple.com/library/safari/documentation/Tools/Conceptual/SafariExtensionGuide/WorkingwithWindowsandTabs/WorkingwithWindowsandTabs.html
              view.location.href = object_url;
            }
          }
          filesaver.readyState = filesaver.DONE;
          dispatch_all();
          revoke(object_url);
        }
      ;
      filesaver.readyState = filesaver.INIT;
      if (can_use_save_link) {
        object_url = get_URL().createObjectURL(blob);
        setTimeout(function() {
          save_link.href = object_url;
          save_link.download = name;
          click(save_link);
          dispatch_all();
          revoke(object_url);
          filesaver.readyState = filesaver.DONE;
        });
        return;
      }
      fs_error();
    }
    , FS_proto = FileSaver.prototype
    , saveAs = function(blob, name, no_auto_bom) {
      return new FileSaver(blob, name || blob.name || "download", no_auto_bom);
    }
  ;
  // IE 10+ (native saveAs)
  if (typeof navigator !== "undefined" && navigator.msSaveOrOpenBlob) {
    return function(blob, name, no_auto_bom) {
      name = name || blob.name || "download";
      if (!no_auto_bom) {
        blob = auto_bom(blob);
      }
      return navigator.msSaveOrOpenBlob(blob, name);
    };
  }
  FS_proto.abort = function(){};
  FS_proto.readyState = FS_proto.INIT = 0;
  FS_proto.WRITING = 1;
  FS_proto.DONE = 2;
  FS_proto.error =
  FS_proto.onwritestart =
  FS_proto.onprogress =
  FS_proto.onwrite =
  FS_proto.onabort =
  FS_proto.onerror =
  FS_proto.onwriteend =
    null;
  return saveAs;
}(
    typeof self !== "undefined" && self
  || typeof window !== "undefined" && window
  || this.content
));
// `self` is undefined in Firefox for Android content script context
// while `this` is nsIContentFrameMessageManager
// with an attribute `content` that corresponds to the window
if (typeof module !== "undefined" && module.exports) {
 module.exports.saveAs = saveAs;
} else if ((typeof define !== "undefined" && define !== null) && (define.amd !== null)) {
 define("FileSaver.js", function() {
  return saveAs;
 });
}

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