Tips for storing a reference to the "this" keyword in a Vue component?

Can you provide some guidance on my approach? Here is an example of a basic Vue component Test.vue:

<template>
    <div>
        Hi from {{name}}
    </div>
</template>

<script>
    let self;

    export default {
        created: function () {
            self = this;
        },
        methods: {
            load() {
                ajax().then((obj) => self.name = obj.data);
            }
        },
        data() {
            return {
                name: 'one',
            }
        }
    }
</script>

In the code snippet, I store the reference to this in a variable called self. This is necessary because the value of this changes within arrow functions, like in this line:

ajax().then((obj) => self.name = obj.data);

The issue I'm facing is that when another instance of the component is created, it replaces the value of the self variable in the previous instance. For instance, if I have two components like this: <test id="1"></test> and <test id="2"></test>, the second component overwrites the self variable of the first one (similarly with v-for).

My question is how can I ensure that the self variable retains the value of this for each instance without being overwritten?

Edit: I understand that I could set self = this in every function, but this is just a simple example with one method. In reality, my component has over 20 functions, so setting self = this in each function is not optimal. I am looking for a way to create a variable during the create call that I can assign once and use throughout the component (similar to using a that variable).

Answer №1

Trying to achieve this is mostly not required.

In JavaScript, it can sometimes be confusing to understand the value of this. However, there are well-known solutions to this common problem.

For problems related to the Vue instance, these solutions include:

Let's walk through an example before jumping to conclusions. Consider this snippet from your source code:

    methods: {
        load() {
            ajax().then((obj) => self.name = obj.data);
        }
    },

When passing a function as an argument for .then(), the value of this inside that function will depend on how you pass it.

In the first scenario (using arrow functions), like you did with arrow functions, the use of self is unnecessary because this inside the arrow function will still refer to the Vue instance.

    methods: {
        load() {
            console.log(this.name);
            ajax().then((obj) => this.name = obj.data);
        }
    },

In the above example, both occurrences of this.name point to the same property. See demo below for clarification.

...

Similarly, in the second solution using a regular function, to ensure this is preserved, you would use .bind(this).

    methods: {
        load() {
            console.log(this.name);
            ajax().then(function (obj) { this.name = obj.data }.bind(this));
        }
    },

Just like before, both references to this.name in this case refer to the same property. See demo below for demonstration.

...

Therefore, within the Vue instance, declaring the self variable is unnecessary.

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