JavaScript函数.prototype.bind() 方法

函数是一组接受输入、进行特定计算并产生输出的语句。在编程中有各种场景，我们需要预先配置this关键字或函数参数，我们可以在 JavaScript 中借助bind()方法轻松地做到这一点。 bind() 方法根据调用它的函数创建一个新函数。使用 bind() 方法，我们可以使用如下所示的语法为函数预先配置this关键字和参数。

句法：

const newFunction = oldFunction.bind(thisArg, arg1, ag2, ..., argN)

使用上面的语法，基于旧函数创建一个新函数，并将 this 关键字设置为thisArg ， 和函数参数预配置为arg1 、 agr2等。下面提到的示例在示例的帮助下演示了bind()方法的使用。

例子：

Javascript

    const car = {
        brand: 'Lamborghini',
    };
 
    // As of now, 'this' keyword refers
    // to 'window' object.
    const printDetail = function (model, topSpeed) {
        console.log(`${this.brand} ${model} has a
        top speed of ${topSpeed} mph`);
    };
 
    // Calling the function without using bind which
    // means 'this' still refers to 'window' object
    // so accessing this.brand will give undefined
    printDetail('Diablo Coatl', 239);
 
    // Creating a new function based on printDetail
    // with 'this' keyword referring to car object
    // so accessing this.brand will give 'Lamborgini'
    const lamboPrintDetail = printDetail.bind(car);
    lamboPrintDetail('Diablo VTTT', 222);
 
    // Creating another function based on printDetail
    // with it's arguments pre-configured and 'this'
    // keyword referring to car object
    const reventonPrintDetail
        = printDetail.bind(car, 'Reventon', 221);
 
    // Since the arguments are preconfigured so we don't
    // need to pass any argument to call this function
    reventonPrintDetail();

输出：

undefined Diablo Coatl has a top speed of 239 mph
Lamborghini Diablo VTTT has a top speed of 222 mph
Lamborghini Reventon has a top speed of 221 mph