JavaScript 中函数.prototype.bind 的用途是什么？

绑定方法：使用该方法，我们可以将一个对象绑定到一个通用函数，以便在需要时给出不同的结果。 bind() 方法将一个对象作为参数并创建一个新函数。所以基本上是绑定函数返回函数。

让我们了解何时使用绑定方法。

bind the object with common function

示例 1：

Javascript

    const gfg = {
        name: "javascript",
        content: "prototype",
        feature: function () {
            console.log(
                `Help in learning ${this.name}.
                The topic is ${this.content}`
            );
        }
    }
 
    // Simple method to feature of gfg object
    gfg.feature();
    console.log()
 
    // Try to bind gfg object property feature
    // to other common function so that it
    // used for later use but it does not
    // happen here
    let b = gfg.feature;
    b();
    console.log()
 
    // Now try to bind object using bind
    // method
    // bind method first argument refer
    // object that's why parameter gfg object
    let c = gfg.feature.bind(gfg);
    c();

Note: Bind different objects to a common function so that each object can access that function and extra functionality to objects so bind function takes any number of arguments.

Example 2: 

Javascript

    const gfg = {
        name: "javascript",
        content: "prototype",
    }
 
    const gfg1 = {
        name: "c++",
        content: "inheritance",
    }
 
    const gfg2 = {
        name: "java",
        content: "applet",
    }
 
    // Function which is binding with different object
    function features(param) {
        console.log(`Help in learning ${this.name}.
        The topic is ${this.content} and
         these are help in ${param}`)
    }
 
    // Binding obj1 abd extra functionality
    let bindfunc = features.bind(gfg);
 
    bindfunc("placement");
     
    // Binding obj2
    let bindfunc1 = features.bind(gfg2);
    bindfunc1("placement");