为什么AngularJS在其isArray函数中不使用instanceof? [英] Why does AngularJS not use instanceof in its isArray function?
问题描述
从AngularJS isArray 来源:
From AngularJS isArray source:
return toString.call(value) === '[object Array]';
他们为什么不去?
return value instanceof Array;
推荐答案
因为如果您从其他 window (例如，另一个框架或iframe，子窗口，父窗口，等等)，它不会是您的窗口中的 instanceof Array 构造函数.
Because if you receive an array from a different window (e.g., another frame or iframe, a child window, a parent window, etc.), it won't be instanceof the Array constructor in your window.
这就是为什么他们在ES5中添加了 Array.isArray 函数转换为JavaScript，因此我们可以停止以困难的方式进行操作，如下所示:
This is why in ES5 they added the Array.isArray function to JavaScript, so we could stop doing it the hard way, which looks like this:
if (Object.prototype.toString.call(theArray) === "[object Array]") ...
各个方面的示例:实时复制
父窗口:
<body>
<input type="button" value="Click To Open Window">
<script>
(function() {
"use strict";
var wnd;
document.querySelector("input").onclick = function() {
wnd = window.open("http://jsbin.com/yimug/1");
display("Opened, waiting for child window to load...");
setTimeout(waitForChild, 10);
};
function waitForChild() {
if (wnd && wnd.sendMeSomething) {
display("Child window loaded, sending [1, 2, 3]");
wnd.sendMeSomething([1, 2, 3]);
}
}
function display(msg) {
var p = document.createElement('p');
p.innerHTML = String(msg);
document.body.appendChild(p);
}
})();
</script>
</body>
子窗口:
<script>
(function() {
"use strict";
window.sendMeSomething = function(something) {
display("Got " + something.join(", "));
display("something instanceof Array? " + (something instanceof Array));
display("Object.prototype.toString.call(something): " + Object.prototype.toString.call(something));
if (Array.isArray) {
display("Array.isArray(something)? " + Array.isArray(something));
}
};
function display(msg) {
var p = document.createElement('p');
p.innerHTML = String(msg);
document.body.appendChild(p);
}
})();
</script>
输出(在子窗口中)( something 是从父级接收数组的参数的名称)
Output (in child window) (something is the name of the argument where it receives an array from the parent):
Got 1, 2, 3
something instanceof Array? false
Object.prototype.toString.call(something): [object Array]
Array.isArray(something)? true
这篇关于为什么AngularJS在其isArray函数中不使用instanceof?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
