JavaScript で setTimeout/setInterval を使用する場合、プロトタイプ メソッドで「この」コンテキストを保持するにはどうすればよいですか?

Preserving "this" Context in Prototype Methods with setTimeout/setInterval

In Javascript, accessing "this" within a prototype method can become tricky when using setTimeouts or intervals. Unlike in Python, Javascript methods lose their context when passed externally. To overcome this challenge, we explore various solutions.

Anonymous Function Wrapper

The most straightforward approach is to wrap the method call in an anonymous function:

<code class="javascript">var that = this;
setInterval(function(){
    return that.baz();
}, 1000);</code>

This ensures that the method call and access to "this" occur simultaneously, preserving the correct context.

Fat Arrow Function Wrapper (ES6)

For implementations supporting fat arrow functions:

<code class="javascript">setInterval( () =&gt; this.baz(), 1000 );</code>

This concise syntax preserves the context from the surrounding function.

Function Binding

Finally, consider using a binding function like Function.prototype.bind:

<code class="javascript">setInterval( this.baz.bind(this), 1000 );</code>

Alternatively, libraries like Dojo provide methods like "hitch" for context binding.

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