Question

此代码来自jquery.validate.js。我认为这是一个自动执行的函数，但我很难解析第二个函数声明的语法。函数（$）{}是第一个函数的参数，即工厂吗？

(function (factory) {
    alert("In jquery.validate.js factory");
    if ( typeof define === "function" && define.amd ) {
        define( ["jquery"], factory );
    } else {
        factory( jQuery );
    }
}(function ($) {
... //body of function
});

Answer 1

这是我们今天看到的常见库模式，起初它让我感到奇怪。花了一段时间才明白发生了什么。

首先，这是一个传入函数的自执行函数。在我们查看操作之前，先看一下构造。

// Self executing function that takes no arguments.
(function () { 
    // Some code here.
})();



// Self executing function that takes an argument.
(function (argument) {
     alert(argument);
})("Hello World");



// Self executing function that takes function as argument.
(function (factory) {
   // Self executing. Executes as soon as the script is loaded.
   // At this point, factory = the function below.
})(function (param) {
   // Not self executing! Must be called.
});

现在我们已经理解了这里发生的事情的构造，让我们来看看这段代码：

// If there is a variable called "define", and that variable is a function, call that function with the paramenter jQuery and pass it the function. This is how we define a library in RequireJS.
if ( typeof define === "function" && define.amd ) {
    define( ["jquery"], factory );
} else {
    // This is how we define the jQuery library everywhere else in the world. We pass the global window.jQuery into the function.
    factory( jQuery );
}

所以现在一起，

// Define jQuery.
(function (factory) {
    // If using RequireJS, define jQuery by calling the define function with the jQuery factory.
    if ( typeof define === "function" && define.amd ) {
         define( ["jquery"], factory );
    } else {
        // Otherwise, just call the jQuery factory.
        factory( jQuery );
    }
}(function ($) {
    // Use JQuery or $.
});

有人可以告诉我这个javascript代码在做什么

1 个答案: