重写 window.alert 并传递多个参数
我试图覆盖 window.alert 以传递多个参数。
请有人解释一下为什么 for/in 将 Array.prototype.tester 的主体继承到列表中？
非常感谢。
Array.prototype.tester = function() {
return 'tester';
}
window.alert = function() {
var args = Array.prototype.slice.call(arguments);
var list = [];
for (var i in args) {
list.push(args[i]);
}
return list.join(', '); // WHY???? alerts: "arg1, arg2, function () { return "tester"; }"
//return args.join(', '); // alerts: "arg1, arg2" expected.
}
alert('arg1', 'arg2');
I am trying to override the window.alert to pass multiple parameters.
Please someone explain me why for/in inherits Array.prototype.tester's body into list?
Thank you very much.
Array.prototype.tester = function() {
return 'tester';
}
window.alert = function() {
var args = Array.prototype.slice.call(arguments);
var list = [];
for (var i in args) {
list.push(args[i]);
}
return list.join(', '); // WHY???? alerts: "arg1, arg2, function () { return "tester"; }"
//return args.join(', '); // alerts: "arg1, arg2" expected.
}
alert('arg1', 'arg2');
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评论（3）
for-in迭代对象的所有可枚举属性，其中包括对象或其原型中定义的任何内容。大多数内置函数都被声明为不可枚举，因此它们在正常迭代期间不会出现。 ECMAScript 5 允许您将自己的属性定义为不可枚举的，尽管我不确定哪些浏览器支持此功能：for-initerates over all enumerable properties of an object, which includes anything defined in the object or its prototypes. Most built-in functions are declared non-enumerable, so they don't appear during normal iteration. ECMAScript 5 allows you to define your own properties as non-enumerable, although I'm not sure which browsers support this:正如 casablanca 所提到的，
for in会迭代您定义的属性位于对象原型链中。要解决此问题，请使用
hasOwnProperty()< /a>.As mentioned by casablanca,
for initerates over properties defined by yourself that are in the objects prototype chain.To fix this, use
hasOwnProperty().window.alert是一个常量函数，您不能直接重新定义它：Javascript 覆盖警报
window.alertis a constant function, you cannot redefine it directly:Javascript overriding alert