Unpacking default function parameters in Vue.js and understanding the 'this' keyword

Is there a way to correctly reference the data object using this when setting default parameters with destructuring in Vue.js?

activated () {
  this.fillData()
},

data () {
  return {
    chartData: {
      distributionInitialData: {
        // data here
      }
    }
  }
},

methods: {
  fillData ({
      must = this.chartData.distributionInitialData,
      nice = this.chartData.distributionInitialData
    }) {
    // do something
    // function doesn't even get here because it gets error:
    // TypeError: Cannot read property 'must' of undefined
    // at VueComponent.fillData (Component.vue?4e6a:230)
    // at VueComponent.activated (Component.vue?4e6a:123)
  }
}

Answer №1

In order to ensure the parameter (Object) has a default value, it is crucial to not set default values for its properties.

methods: {
  fillData ({must, nice} = {
      must: this.chartData.distributionInitialData,
      nice: this.chartData.distributionInitialData
    }) {
    // do something
  }
}

Improved based on Bergi's recommendation.

methods: {
  fillData ({
      must: this.chartData.distributionInitialData,
      nice: this.chartData.distributionInitialData
    } = {}) {
    // do something
  }
}

If you're interested, you can check out a simple CodePen example.

Answer №2

It is possible.

updateData ({ required, good}) {
    required = required || this.graphData.defaultDistribution
    good = good || this.graphData.defaultDistribution

    // perform an action
}

Answer №3

Vue's method binding to components can cause issues due to access to the instance. While the function definition lacks this access, you can utilize this within it.

An easy fix is to check for undefined values immediately and set them based on default preferences.

fillData({ must, nice }) {
    if (must === undefined) must = this.chartData.distributionInitialData;
    if (nice === undefined) nice = this.chartData.distributionInitialData;

    // additional code here
}

You could also experiment with arrow functions to potentially resolve this issue. Arrow functions were designed to be more explicitly bound to this. Here's an example:

fillData = ({ 
    must = this.chartData.distributionInitialData, 
    nice = this.chartData.distributionInitialData 
}) => {
    // additional code here
}

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