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5 Décembre 2022 à 08h01 - 3503 affichages

How to bind a class method in JavaScript

If you're looking to javascript bind class method, you've come to the right place. We'll show you how to do it using the built-in bind() method.

The bind() method is used to create a new function that, when called, has its this keyword set to the provided value. In other words, it allows you to "bind" a function to an object.

We can use the bind() method to create a new function that always uses a particular object as its this value. This is especially useful when working with event handlers.

For instance, let's say we have an object with a method called handleClick(). We want to set this method as an onclick handler for a button, but we don't want the method to be called in the global scope.

We can use the bind() method to create a new function that will call handleClick() with the correct this value:

var button = document.querySelector('button');

button.addEventListener('click', obj.handleClick.bind(obj));

Now when the button is clicked, the handleClick() method will be called with obj as its this value.

The bind() method can also be used to partially apply arguments to a function. This is especially useful when working with callback functions.

For instance, let's say we have a function that takes two arguments: a URL and a callback function. We want to create a new function that will call this function with a predetermined URL.

We can use the bind() method to do this:

function loadData(url, callback) {
 // code to load data from the URL
}

var boundLoadData = loadData.bind(null, 'https://example.com/data.json');

boundLoadData(function(data) {
 // data is loaded
});

As you can see, we passed null as the first argument to bind(). This sets the this keyword to null when the new function is called.

We also passed 'https://example.com/data.json' as the second argument. This sets the first argument of the original function to this value.

When we call boundLoadData(), the callback function is passed as the second argument to loadData().

The bind() method can be used in conjunction with the call() and apply() methods to set the this value in a function.

For instance, let's say we have an object with a method called foo(). We want to call this method with a different this value.