如何等待FileReader onload首先完成

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    imageExists(url, callback) {
      var img = new Image();
      img.onload = function () { callback(true); };
      img.onerror = function () { callback(false); };
      img.src = url;
    isImageCorrupt(file): boolean {
      var reader = new FileReader();
      var isCorrupt = false;
      reader.readAsDataURL(file);
      reader.onload = (e) => {
        this.imageExists(e.target.result, (exists) => {
            if (exists) {
                isCorrupt = false;
                // Image is not corrupt
            } else {
                isCorrupt = true;
                //Image is corrupt
    return isCorrupt;
   }

 isImageCorrupt(file): Promise<Boolean> {
    return new Promise((resolve) => {
        var reader = new FileReader();
        reader.onload = (e) => {
            var img = new Image();
            img.onload = function () {
              resolve(false);
            img.onerror = function () {
              resolve(true);
            img.src = <string>e.target.result;
        reader.readAsDataURL(file);
}

    isImageCorrupt(file): Promise<boolean> {
      return new Promise<boolean>((resolve,reject)=>{
      var reader = new FileReader();
      reader.readAsDataURL(file);
      reader.onload = ()=>{
      var img = new Image();
      img.src = reader.result;
            img.onload = function () {
              resolve(false);
            img.onerror = function () {
              resolve(true);
reader.onerror=()=>{reject(true)}
       isImageCorrupt(yourFile).then((result)=>{/*HERE USE RESULT*/},(error)=>{HERE USE ERROR RESULT})

isImageCorrupt(file): Promise<void> {
          return new Promise<void>((resolve,reject)=>{
          var reader = new FileReader();
          reader.readAsDataURL(file);
          reader.onload = ()=>{
          var img = new Image();
          img.src = reader.result;
                img.onload = function () {
                  resolve();
                img.onerror = function () {
                  reject();
    reader.onerror=()=>{reject()}

如何等待FileReader onload首先完成

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