javascript - IsPlainObject，东西？

Question

这个fn是吗:

function isplainobj ( obj ) {
    return Object.prototype.toString.call( obj ) === "[object Object]";
}

做与 jQuery 相同的事情:$.isPlainObject() ？

Answer 1

不，事实并非如此。

这是它的实现:

isPlainObject: function( obj ) {
    var key;

    // Must be an Object.
    // Because of IE, we also have to check the presence of the constructor property.
    // Make sure that DOM nodes and window objects don't pass through, as well
    if ( !obj || jQuery.type(obj) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {
        return false;
    }

    try {
        // Not own constructor property must be Object
        if ( obj.constructor &&
            !core_hasOwn.call(obj, "constructor") &&
            !core_hasOwn.call(obj.constructor.prototype, "isPrototypeOf") ) {
            return false;
        }
    } catch ( e ) {
        // IE8,9 Will throw exceptions on certain host objects #9897
        return false;
    }

    // Support: IE<9
    // Handle iteration over inherited properties before own properties.
    if ( jQuery.support.ownLast ) {
        for ( key in obj ) {
            return core_hasOwn.call( obj, key );
        }
    }

    // Own properties are enumerated firstly, so to speed up,
    // if last one is own, then all properties are own.
    for ( key in obj ) {}

    return key === undefined || core_hasOwn.call( obj, key );
},

它检查它的类型是否是对象，它是否有构造函数以及它的属性是否是自己的属性。

例如，对于您的函数，类的实例将返回 true，但在这种情况下，因为它有一个构造函数，它将返回 false。