Javascript IN运算符兼容性 [英] Javascript IN operator compatibility

问题描述

有人可以告诉我哪个ECMA版本的IN运算符可用以及哪些浏览器（版本）支持它？

Can someone tell me since which ECMA version the IN operator is available and which browsers (versions) support it ?

说明：

IN运算符可以像下面一样使用：

The IN-operator can be used like the following:

var myObject = {
    Firstname: 'Foo',
    Lastname: 'Bar'
};

if('Lastname' in myObject){
    // Lastname is an attribute of myObject
}

推荐答案

它在 ECMAScript第3版。它适用于IE 5.5+以及所有正在使用的Firefox，Chrome，Opera和Safari版本。

It is defined in ECMAScript 3rd edition. It is available in IE 5.5+ and all in-use versions of Firefox, Chrome, Opera and Safari.

您可以安全地使用它，因为它知道它会起作用。

You can use it safe in the knowledge that it will work.

使用它来检查事件支持时，你应该小心谨慎。除旧版Firefox以外的所有实现都支持元素中的eventname作为DOM事件的测试。

You should err on the side of caution when using it to check event support. All implementations except older Firefox versions support "eventname" in element as a test for DOM events.

"onclick" in document.body; // -> false in old Fx, true in others
document.body.setAttribute("onclick", "");
typeof(document.body.onclick == "function"); // -> true in Fx

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