Unable to assign the string obtained from the reader.result to a variable as it is returning null

I'm currently facing an issue with the code below

When I try to console.log image.Url in the outer function, it returns null even though it should return a string from the reader.onload function

Here is the complete code snippet:


export default {
  data() {
    return {
      item: {
        image: null
      },
      imageUrl: null,
    };
  },

  methods: {,
    uploadImage(e) {
      let image = e.target.files[0];
      const reader = new FileReader();
      reader.readAsDataURL(image);

      reader.onload = function(){
        this.imageUrl = reader.result
        console.log(this.imageUrl)
        // this.setImageOne(this.imageUrl)
      }
      console.log(this.imageUrl)
      

    },

Issue has been resolved. Thank you for all the assistance.

Answer №1

The sequence of events is not unfolding as anticipated.

Here is the actual order of occurrences:

  1. uploadImage() function is invoked
  2. The second console.log executes and shows imageUrl as null (since the callback function is registered for the onload event)
  3. The onload callback triggers, setting the value of imageUrl
function(){
        this.imageUrl = reader.result
        console.log(this.imageUrl)
        // this.setImageOne(this.imageUrl)
      }

It's important to note that this function is not executed upon declaration. JavaScript only calls the provided callback function when the onload event takes place. It first registers this callback before moving on to the console.log statement.

To utilize the value of imageUrl, it should be done within the callback function itself.

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